Craig Kimbrel has dominated the final three outs of major league baseball games for seven seasons now. I’d argue he’s been more dominant than any reliever over that stretch, including Aroldis Chapman (who many view as the game’s top closer). But over their careers no one active today — including Chapman — has been more dominant than Kimbrel, especially this season.
Among relievers with at least 200 innings over the past 7 seasons, no one has a lower FIP, xFIP, or batting average against than Kimbrel. He is also second among relievers in strikeout rate with 41.4 percent, behind only Aroldis Chapman and by less than one percent, although Kimbrel easily beats Chapman in walk rate by over two percent. Meanwhile only Zach Britton and Wade Davis have a lower ERA during that time than Kimbrel, and they’ve both pitched over 100 innings less than Kimbrel has. In fact, Kimbrel has the seventh-most innings pitched in relief since 2011 and also has highest WAR over that period as well. He’s been the most dominant closer of this generation, no doubt about it.
As Kimbrel continues his dominance, the next potential Craig Kimbrel has emerged this season in the form of Milwaukee Brewers closer Corey Knebel. The similarities are striking, and I’m not just talking about their initials and quasi-rhyming last names. The level of dominance Knebel has displayed feels eerily similar to what Kimbrel began showing us almost a decade ago.
The most obvious similarity is the blazing fastball. Kimbrel’s regularly touches triple digits and this season has averaged 98.7 mile per hour according to Pitch Info. Knebel is just a touch below that, sitting at 97.7 miles per hour, although it has experienced a huge uptick this season as the chart below shows.
The second similarity is the knuckle-curve and the fact that it’s their only secondary pitch. Kimbrel features a hard knuckle-curve that sits at 87.7 miles per hour and sometimes even touches 90 miles per hour, while Knebel throws a much more typical knuckle-curve at 80.6 miles per hour that can reach as high as 83.
The pitch types are only the tip of the iceberg, as Knebel’s 2017 strikeout rate of 42.6 percent is not only currently surpassing Kimbrel’s career strikeout rate of 41.6 percent, but is also the second-highest rate among all relievers this season behind only Kimbrel, who is striking out 50 percent of batters he faces.
Knebel is also seventh in ERA- at 35, 11th in FIP- at 49, and 12th in xFIP- at 64. He ranks slightly behind Kimbrel in all three categories this season, but it’s safe to say Kimbrel is having a career year, so it’s hard to hold Knebel to that high of a standard this early in his career. Knebel compares more favorably to Kimbrel’s career numbers in ERA-, FIP- and xFIP-: 46, 47, and 52 respectively.
However the similarities don’t extend to the process behind those numbers. Kimbrel has been getting it done with pure swings and misses, as he has the highest whiff rate in the league at 20.8 percent. Knebel’s swinging strike rate is quite low, only 13.2 percent, which is 68th among 187 relievers. Not only is Knebel’s whiff rate low, his swing rate is also low, ranked 11th lowest among those same 184 relievers at 41.7 percent.
So what’s responsible for a strikeout rate over 40 percent with such a low swing rate? A notably low contact rate of 68.5 percent, ranked 23rd lowest, and lots of called strikes means that Knebel doesn’t need as many swings as his peers.
The unbelievably high whiff-per-swing rate on both of his pitches means that, although he’s not getting a lot of swings or swings and misses, hitters are rarely making contact with his pitches. His whiff rate on all swings is 34.9 percent, according to Baseball Savant, while only 7.9 percent of the 404 total swings against him resulted in a base hit. The chart below also shows the number of whiffs per swing each pitch has resulted in.
The second main cause for Knebel’s strikeout rate is a huge number of called strikes. Of his 977 total pitches this season, 198 of them have been a called strike, over 20 percent. Additionally, more than one third of Knebel’s pitches that weren’t swung at were called strikes. The chart below shows the pitch type breakdown of all Knebel’s pitches, including the high number of called strikes.
Of the 198 called strikes, 88 of them have come off the knuckle-curve. While it’s surprising that almost 45 percent of Knebel’s called strikes are coming off his breaking ball, the pitch’s movement and Knebel’s solid command of it leaves a hitter with no choice but to take the pitch and hope it’s not a strike, or risk swinging at a pitch that could end up outside the strike zone.
Knebel’s knuckle-curve has the third highest vertical movement among relievers who’ve thrown at least 100 curveballs this season and is 16th in horizontal movement among the same relievers. Add that to an above average spin rate of 2,540 RPMs (ranked 29th out of 77 relievers) and you have the recipe for an untouchable pitch.
Only 17 of Knebel’s 274 knuckle-curves have been put into play and only five of those resulted in base hits, four singles and one double by Baltimore Orioles outfielder Joey Rickard in a 2-2 count.
A major factor in the success of any pitch, no matter the movement, velocity or whiff rate, is solid command. Knebel has shown an ability to command his knuckle-curve in whatever way the situation requires. The series of heatmaps below show the location of the knuckle-curve in a variety of situations.
Knebel’s fastball is also a top-tier pitch, ranked 19th in velocity league-wide, as well as 28th in vertical movement and 8th in whiffs per swing (at 33.93 percent). He’s done an outstanding job of keeping the fastball out of play as well: only 75 of Knebel’s 691 four-seamers were put into play, and of those 75 only 27 of them resulted in base hits, including three home runs and six doubles.
What’s made the four-seamer successful has been Knebel’s location of the pitch at the top of and along the edges of the strike zone. That makes it a very difficult to get a hit off the pitch, especially when combined with the high velocity Knebel has been featuring this season.
One important point to note is that when Knebel is behind in the count he mainly relies on his fourseamer; he’s thrown the pitch 75 percent of the time when behind, or on 242 of his 322 total pitches. But when he falls behind and throws the four-seamer, he doesn’t give into the hitter at all, as show by the chart below. Knebel still locates a majority of the pitches around the edges to keep the ball out of play, and only occasionally puts one down the middle.
This is a big reason why he’s walked 25 batters with the four-seamer out of his 31 total walks this season. The high number of walks with his fastball has pushed his walk rate to 14.4 percent, which is sixth highest among relievers. Given that it’s a product of his refusal to grove a pitch even when behind in the count, not of poor command, that’s an acceptable trade-off.
With three-quarters of the season behind us, Knebel has put up some incredible numbers — especially the lack of balls put in play and called strikes — thanks to the command of his two pitches. If he continues performing to a high level in those areas, or at least adjusts once batters start putting more balls into play and taking less called strikes, it’s hard not to see Knebel dominating for many years to come.
At the very least the Milwaukee Brewers have found themselves a long-term option at closer who is already one of the game's best. Or they may have themselves one of the most coveted trade pieces at some upcoming trade deadline, depending on where they’re heading with the organization.
Regardless of what happens beyond this season, the Brewers are currently in the middle of a postseason chase, and Knebel has surprisingly turned into one of their most valuable players for the stretch run and possibly the postseason.