Bringing an outfielder into the infield is rare, but it does happen. It tends to be based on the fielders and the situation, and not the batter at the plate. The classic scenario: home team has the winning run on third with less than two outs, in the ninth inning or later. A ball on the ground could have the runner on the move; the outfielders play in, because although a fly out will give the fielder a bit more time (as the runner waits to tag up), an outfielder who is not playing more shallowly than normal is unlikely to nail the runner at the plate.
One situation that fit this description in 2014 found the Dodgers using a five-man infield. Here's TrueBlueLA's description of that inning (complete with GIF) and a different view at CBSSports. Four men all between second base and first is completely bizarre. But a five-man infield need not look like that, or be tethered to that one ultra-rare type of situation.
Launch angle: a game of darts
As a hitter, which skill is more important: accuracy or precision? Both are necessary for a hitter to find regular success, but it may be that accuracy can be more easily changed. Using the old dartboard illustration, if a hitter has a loose grouping of darts that are centered on the bulls-eye, we might call him accurate, but not precise (or we might just call him Dan Uggla). If he has tight grouping of darts well off the bulls-eye, he may be able to make an adjustment that will leave him both precise (the tight grouping) and accurate.
That may be why we see few qualified hitters with obscene ground ball to fly ball ratios. If a hitter is consistently missing under the ball, maybe he can simply aim higher; the opposite if he's beating the ball into the ground. Of 146 qualified hitters from the 2014 season, the 10th-ranked GB/FB (DJ LeMahieu) was 2.41; 10th from the bottom had a GB/FB ratio of 0.77 (Edwin Encarnacion). The league GB/FB rate was 1.28, and 118 of those 146 qualified hitters were within 0.50 of that mark.
In other words, not a lot of variation. But what if that weren't the case?
If there were a hitter who only hit fly balls, would you keep four men stationed in the infield? Chances are, someone would be in the neighborhood to catch the rare infield fly. Except in situations with multiple runners, three men could theoretically cover the three bases. And a fourth outfielder or short fielder could be death to fly balls.
Conversely, a hitter who only hit ground balls might make a team want to stack the box in the infield. With shifting on the rise throughout the sport, is this something we're likely to see more often?
In which we meet our hero: Ben Revere
I'm reasonably satisfied that if a team knew a particular hitter would definitely hit a ground ball, they'd move an outfielder to the infield. Maybe it would still depend in part on the situation — for instance, with two outs and no runners, one might be less worried about giving up a freak-occurrence triple. But we're talking about the strategy being dictated by the tendencies of the batter. If a 100% ground ball rate makes a five-man infield smart (a premise I'm accepting but with which you might disagree), then whether or not a five-man infield makes sense as a shift for an individual batter could be a question of thresholds.
Let's use the groundballiest of ground ball hitters to see if he exceeds a five-man infield threshold. Ben Revere sported a 4.51 GB/FB rate last season, worlds away from the #2 man in that category, Nori Aoki (3.63 GB/FB). His ground ball percentage was 64.7%. And thanks to a very respectable 21% line drive rate, all of those ground balls sunk Revere's fly ball rate all the way down to 14.3%.
14.3%! Revere had 626 plate appearances in 2014, but hit just 78 fly balls. Heck, two of those even went out of the park. And 2014 wasn't out of character for Revere; he had just a 59.3% GB% in a shorter 336-PA season in 2013, but for his career, 65.4% of Revere's batted balls have been on the ground. It may be that in Revere, we've found one of the rare hitters who is precise, but inaccurate in terms of launch angle.
More interesting yet, it's when he's hitting the opposite way that Revere hits balls in the air. His GB/FB ratio is a whopping 5.74 up the middle, but an obscene 14.11 to his pull side; going the opposite way, he hit "just" 1.67 ground balls for every fly ball. Revere had a difficult time hitting balls in the air, but it looks like he couldn't hit one to his pull side to save his life. Here's his spray chart from 2014:
What if Ben Revere hit with the right fielder missing?
Counting those two doubles up by the two black home run marks out of right field, Revere hit seven fly balls to his pull side in 2014. Four of them had a hang time of at least 4.5 seconds. It's really line drives that a team has to be concerned about in right field (17), but all but three of those fell in for hits anyway. There were about sixteen ground balls fielded by right fielders that almost definitely would have gone for more bases if there was no right fielder, but... what would the damage have been if there actually was no one in right field?
As with many alternate universe questions, we're off book now. For our back-of-the-envelope math, let's just say that four fly balls would not get caught, and would become doubles. Let's say all sixteen ground balls fielded by right fielders would have become doubles, approximating doubles instead of singles. And let's say the three line drives that were caught would become triples, and the ones not caught would also be triples instead of singles (7) or doubles (7). Here's the change in terms of runs, using Tango's run value of events table:
|Flyball outs becoming doubles||1.05 (0.77 instead of -0.28)||4||4.2|
|Groundball singles becoming doubles||0.3 (0.77 instead of 0.47)||16||4.8|
|Lineouts becoming triples||1.42 (1.09 instead of -0.33)||3||4.26|
|Line drive singles becoming triples||0.62 (1.09 instead of 0.47)||7||4.34|
|Line drive doubles becoming triples||0.32 (1.09 instead of 0.77)||7||2.24|
There are several reasons why I can't do what I just did. For one thing, there's no reason to think that Revere would have hit balls in exactly the same spots if there were no right fielder. Also, there's no reason to think that if a team's right fielder suddenly disappeared with Revere at the plate, the team's other fielders might not compensate in some way; the center fielder might at least shade to right instead of shading to left. This is not an exercise in reality. Nonetheless, it might give us a somewhat reliable gross estimate. Even in the case of Revere, who rarely peppers right field with batted balls, removing a fielder can have disastrous consequences. Comparing apples to some other variety of apples, Revere had 64 Runs Created in 2014. The addition of 20 runs, then, is nothing to shake a stick at (and is about 2 wins' worth of runs, to boot).
What if the missing fielder played elsewhere?
What we're really curious about, though, is whether moving a fielder around would save more runs than having a fielder in right would save. And this is where our junk math gets even junkier.
Where would the extra man even play? You could put in one extra infielder (assuming the player is capable of that), scrunching everyone together just a bit more, and hopefully stealing away some of Revere's 92 (!) ground ball hits. But the five-man infield would need to turn 28 or more of the ground ball hits into outs in order to break even with the above nearly-20 extra runs from the lack of a right fielder. That seems dubious, although I know of no way to test that.
How about a designated bunt defenseman? He could play on the side on which the pitcher is least comfortable fielding. Having someone in further seems promising: Of those 92 ground ball hits, 26 were infield hits, and 4 were bunt hits. Sadly, an extra fielder in the infield would be unlikely to turn all of those singles into outs; even if you believed the fiction that all of the infield hits were "short" and that the fielder could turn everything in his direction into outs, placing him between the pitcher and the third base line will not make fielding softly-hit ground balls to the first base side any easier. Positioning him to optimize the pitcher's possible contribution could mean more than half get fielded, but this plan would have the fielding team fall woefully short of the 28 ground ball hits that would need to be converted to outs to make up for the lack of a right fielder.
What of pushing someone to the back of the infield? Here, we might have something more promising. Here's another Revere spray chart, this time by hit type:
As is probably the case for most hitters, Revere's hit locations for his singles almost look like three stripes running away from the infield — one in the hole between third and short, one up the middle, and one between second and third. Scrunching five infielders together in the infield might replace that pattern with four smaller trickles. But what if, by moving the right fielder to the edge of the grass, you could take away one of the three stripes above?
Revere hit 129 ground balls to the right field side in 2014, 31 of them hits. Center? 154 grounders, 38 hits. And although we saw that Revere does hit more fly balls to the opposite field, he still hit 69 grounders in that direction, with 24 falling in for hits.
The right idea, then, might be to plug a fielder in behind the second base bag. That's the stripe with the most hits, but it's also the stripe with the fewest hits that didn't go as far as the base paths. By my count, 4 of the 24 left-side ground ball hits never went any further than the infield grass (probably the bunts). Maybe the third baseman would be playing a bit closer if there were someone in the third-shortstop hole, but that might only make a small difference. It's a similar story to Revere's pull side: 4 of the 31 ground ball hits in that direction never made it as far as the baseline between first and second.
So that's just 20 hits that could get saved in the left field stripe, and 27 in the right field version. If all of the ground ball hits to the right field side got saved, you might break even by moving the right fielder all the way up to the edge of the grass. But that's a stretch.
That center field stripe, though. Despite the fact that second base is farther from home than first or second, just two hits fell in in front of the base paths. Presumably, the pitcher is partly responsible for that. But what if you put the extra fielder behind second base (slightly to one side, so that the pitcher doesn't act as a screen)? You might not get all 36 remaining ground ball hits up the middle turned into outs. You might get some number in the 20s, however; and by placing the fielder there, you might squeeze out the second baseman and shortstop just enough to snag a couple of extra ground balls from the other two stripes. It could work, but it would be close.
Not so fast: the human element
Shifting is all about optimizing. Jeff Wiser, my partner in crime, has compared it to stacking the box against a football team great with the run but poor with passing; taking away the run might give the other team's offense an "advantage" in the passing game, but conventional wisdom holds that in that situation, forcing the other team to rely more on passing is already in itself some small victory.
Fast players tend to have higher BABIPs, and I don't think I'm claiming anything controversial if I say that speed helps turn batted balls into hits much more easily in the infield than in the outfield. The BABIP advantage for fast players is really about ground balls. Ben Revere is fast. Can we really blame him for hitting so many ground balls? After all, he sported a .330 BABIP in 2014, well above the league average mark of .301 for non-pitchers. Maybe Revere is doing this on purpose. Many of his hits were line drives, of course, but Revere had a .266 batting average on ground balls, quite a lot better than his .155 average on fly balls. The only way to outrun a catch is if you're the one doing the catching.
So is Revere doing this on purpose? It can be difficult to try measuring a batter's efforts to stay away from his pull side, but there is a pretty good test for whether he is avoiding fly balls by choice, or because he just struggles to hit them.
Ben Revere has been at the plate 60 times in his career with a runner on third and fewer than two outs. He's hit just five sacrifice flies, with two flyouts and three doubles. In a situation in which Revere had every incentive to hit a fly ball, he did so just 16.7% of the time. His career fly ball rate is 14.3%. The league average fly ball rate for non-pitchers in 2014 was 34.7%. It's not a huge sample from which to judge, but it's some evidence that Revere would have trouble hitting fly balls even if he had extra incentive to do so. From Baseball Savant, here's Revere's career spray chart in runner-on-third, fewer-than-two-outs situations:
There's no way to know if Revere could pull more fly balls in the absence of a right fielder and the presence of another man in the infield, and there's no way to be sure that his hits would tend to fall in the same places regardless of whether defenses shifted against him. But I think there is some evidence to suggest that his astronomical ground ball to fly ball ratio is less about choice and more about (a lack of) skill, even if his superior BABIPs on ground balls might lead him or the Phillies to not worry too much about it.
Our back-of-the-envelope, alternate universe study leads me to think that a five-man infield might be a slightly better strategy against Ben Revere than leaving fielders where they might normally play. It's a close enough call, however, that it doesn't seem likely to be advantageous against other hitters from the list who qualified for the batting title last year.
Against Revere, one might play the third baseman a smidge closer to home plate than he otherwise would (which would already be a bit closer, in all likelihood), adjust the shortstop four or five feet toward the hole, put the second baseman up the middle on the edge of the outfield grass, and move the first baseman six or seven feet toward first base (I'd guess that the outfielder moved to the infield would man first base). The center fielder could shade thirty or forty feet to right, with the left fielder more or less staying in the same position.
Obviously, this might make particular sense if the pitcher also had a high ground ball ratio, and even more sense if he tended to pitch away when facing left-handed batters like Revere. It also would make much more sense if the team had an outfielder who was comfortable at first base, and was playing a first baseman and two outfielders with plus range. A team with two outfielders with plus range could afford to shade one to right, as some of the fly balls with the longest hang times would probably be in an overlap for those two fielders anyway. If the outfielder you moved was a Martin Prado or Ben Zobrist, all the better; they could play the up-the-middle or second baseman's part with little interruption in service.
That's a lot of ifs, and a lot of work. It's also a lot to risk; since we're talking about just Ben Revere or just a few hitters in terms of position players, an opposing team would essentially be experimenting on their own clock, with the principal benefits possibly felt by the hitters' teams' subsequent foes.
But there could be something here, especially in the National League. If some back-of-the-envelope calculations make it look like a Ben Revere ground ball percentage is right on the threshold of a five-man infield being worth it, ground ball percentages greater than that level could call for that kind of shift. And there are players like that: pitchers.
All told, pitchers had a 63.4% ground ball percentage as batters in 2014, a very Revere-like total (although their fly ball percentage was not quite as low). Weed out some of the best-hitting pitchers, and you might have a group of pitchers with an even more obscene ground ball percentage. For two or three plate appearances in most games, NL clubs could see a five-man infield as a fairly significant advantage. It won't happen in April, but it may be the case that in the not-too-distant future, we'll start to see some five-man infields in baseball not for reasons of game situation, but for reasons of the batter at the plate.
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Ryan P. Morrison is a writer and editor at Beyond The Box Score. He writes about the Arizona Diamondbacks at Inside the 'Zona, and talks D-backs and sabermetrics with co-author Jeff Wiser on The Pool Shot. Follow him on Twitter: @InsidetheZona.