Ground balls and the baseball life cycle

Let's face it, baseball consists of essentially three career phases: getting better, holding steady, then getting worse. All players decline, and it's inevitable. The "getting better" phase takes a long time if you think about it; something like 20-25 years of a player's baseball days are spent improving. If he's lucky, he'll "hold steady" for a few years, perhaps three to five. Then comes the beginning of the end as all players eventually "get worse." It's all part of the baseball life cycle, and literally no one's escaped it.

Now, each player has a different profile and attains his value in a unique way as there's simply no one way to be a good baseball player. For position players, some do it with the glove, some do it with the bat, and some do it with both. It must be nice to be able to master both categories, but for players who amass most of their value with the bat, they don't have a whole lot to contribute once the offense goes. The "don't put all of your eggs in one basket" thing sounds good until you try to play shortstop or catcher. I'm assuming it's quite a lot harder than it looks, and it looks really hard. For some, the bat is the ticket to a big league future until it's no longer viable.

So how do we evaluate the shift when players who rely on the bat start to trend downward? One way might be to look for a decrease in power as hitting for power is a big component of amassing positive offensive value. It's tough to gauge power, but we have some metrics capable of measuring this. Slugging percentage (SLG) probably isn't the best way, but it can be a decent approximation in a pinch. Isolated power (ISO) is better if you've got it in your repertoire. Here at Beyond the Box Score, Dan Weigel and Steven Silverman recently rolled out something potentially even better with weight isolated power (wISO). You can pick your poison, but there are definitely options out there for tracking a player's power.

Another option is to look directly at batted ball type changes. As Eno Sarris wrote early in the 2014 season, a significant increase in ground balls hit might be a sign of that decrease. He compared all hitters' 2013 ground ball rate to that of their early 2014 rates and noted the changes. That's a great start, but I wanted to take a slightly larger look. For starters, we now have an entire season's worth of data to look at for 2014. Also, I wanted to compare the 2014 results to each players' 2011-2013 rates so as to avoid some weird seasonal blip on the radar. By taking a longer look and comparing it to the player's 2014 production, we should have a good idea of who's batted ball profile is really changing.

Luckily, I ran these numbers for all 2014 qualified hitters (excluding rookies). A handful of players with a long history of production jumped off the page as hitting significantly more grounders, signaling a drop in power and, likely, a drop in overall offensive production. First, let's look at who's ground ball rate increased significantly this season as compared to years past, then try to categorize them.

Okay, after looking at 30-ish guys, some trends emerge. I'll place the bulk of these players in a few general buckets below.

Expected Decline

These players are generally old and, like everyone else, getting older. For them, they're on the decline and that's expected. This doesn't mean that they're worthless but instead that the golden years are likely gone. Our leader, Kurt Suzuki, belongs here, as do some older sluggers like Robinson Cano, Albert Pujols, Miguel Montero, Torii Hunter, Ryan Braun, Jose Bautista, Allen Craig, Howie Kendrick and others. For these guys, the power isn't going to increase, only fade away as their value slowly subsides. How long can they hold onto it? That's clearly unclear, but most of the players in this category still have value, just not as much as they used to and it's unlikely to ever increase in the future.

More Grounders May Be A Good Thing

I'm looking at you, fast guys! Dee Gordon hitting the ball on the ground only makes sense given his speed. Similar things can be said for Ben Revere, Adam Eaton and maybe even the completely punchless Adeiny Hechavarria. For these guys, putting the ball in the air is generally a bad idea and while they may not be true offensive forces, hitting balls on the ground may give them the best chance for success. In some cases this has worked well (Gordon, Eaton), and in others it doesn't seem to be helping at all (Hechavarria). The alternative is probably a bunch of weak pop-ups, though, and that's not advisable.

Genuine Concern

What do we do with players who should be hitting their prime, yet their power seems to be drying up? I'm talking about guys like Desmond Jennings, Jay Bruce, Jason Kipnis, Andrelton Simmons and Evan Longoroia. None are truly old enough to fit into that slow-decline area, yet they're showing an increased number of grounders. Also, all of these players showed a drop in ISO in 2014:

So why the increase in grounders and the decrease in power? For Jason Kipnis, it could be a function of nagging injuries that he attempted to play through, even though they did cost him some DL time. Evan Longoria, on the other hand, finally played a full season but was not the same force that we might expect him to be, posting his lowest wRC+ of his career (107) over 162 games. Jay Bruce notably struggled all season long and there really isn't a great explanation as to why. He swung at far fewer pitches this season, but his power drop (especially that seen in the second half) is a bit mysterious. The Braves attempted to make Andrelton Simmons more productive at the plate by having him hit the ball on the ground, but things clearly didn't work out as planned, and now it's unclear if he progresses going forward. Desmond Jennings hit more ground balls but wasn't punished like the others. Still, the grounders aren't necessarily a great thing for him as his overall offensive production dipped this season.

Do these players ditch this trend in 2015? As critical components to their respective teams, this could be a huge red flag that suggests that these players are already going in the wrong direction. Then again, it could be a matter of getting healthy (Kipnis), changing their approach at the plate (Simmons and Bruce) or improving in some other way. All baseball situations are dynamic and the offseason gives teams and players a chance to address in-season deficiencies. Now may just be the time to reverse these puzzling and detrimental changes.

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Given the life cycle of baseball players, we can see some players hitting more grounders that are clearly in the "getting worse" phase of their careers, usually due to age. Some might actually still be "getting better" as they find the right mix of batted ball types to maximize their overall game, in this case plus-plus speed. Others are in a weird spot where they should be "holding steady" through their primes but just aren't for some reason. The increase in ground balls hit isn't helping them, no matter what is ultimately leading to this shift in batted ball outcomes. These players are the most intriguing type and could do one of two things: either become great bounce-back types or continue to fade. The ground ball rate for these players in particular is definitely something to watch for as we move into 2015.

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Jeff Wiser is a featured writer at Beyond the Box Score and co-author of Inside the 'Zona, an analytical look at the Arizona Diamondbacks. You can find his work on craft beer at BeerGraphs and follow him on Twitter @OutfieldGrass24.