Tom Koehler was expected to be an odd man out in the Miami Marlins rotation in 2014. With the team set four-deep with Jose Fernandez, Nathan Eovaldi, Henderson Alvarez, and Jacob Turner, the 27-year-old Koehler was considered an afterthought for the franchise. This was especially true given the fact that Andrew Heaney was set to arrive in the big leagues any minute now after a strong 2013 showing.
But things did not go as planned for the rotation. Fernandez got hurt, Miami did not get the performance it wanted out of Turner, and the team struggled to find a fifth starter for the rest of the year. Meanwhile, only Eovaldi and Koehler remained healthy and able throughout the season, and that forced Koehler into a second year of unexpected full-time starting duty. After throwing 143 innings last year, Koehler went the distance in the rotation in 2014, putting up 32 starts and tossing 191 1/3 innings, both career highs.
The Marlins and Koehler had to be pleasantly surprised with the results. Koehler's career high came along with an improvement in his strikeout rates, as he whiffed 19.1 percent of batters faced this season. Surprisingly, that ended up being the best mark among the starters on the Fish. He walked the same number of hitters as he did last year, and he ended up allowing fewer home runs by a smidgen, leading to an overall better season. Koehler's 3.81 ERA and matching 3.84 FIP were both career bests and nice improvements over last year's performance.
How did Koehler pull it off? An improvement on his fastball appears to be part of the story. After possessing one of the worst fastballs by linear weights runs last season, Koehler's heater was decidedly closer to average this year. He threw some of his fastballs with a little more sink this year, but overall the velocity remained similar to last season. The addition of more sink improved the ground ball rate (though his overall ground ball rate actually decreased this season) and he also got a few more whiffs from the pitch; Koehler induced swings and misses in 15.6 percent of pitches swung at that were classified as four-seamers by Brooks Baseball.
Photo by Steve Mitchell, USA TODAY Sports
You can combine that with Koehler's relatively successful breaking pitches and see why he was able to lead the team in strikeouts. Unlike Eovaldi and Alvarez, who depend on their fastballs for most of their success and have marginal breaking pitches, Koehler actually has two workable secondary offerings in a slider and a curveball. The slider got whiffs on 38 percent of swings for the second straight season, but it was the curveball that once again helped bail Koehler out. Not only did he get whiffs on it in 24 percent of swings, but hitters made weak contact on it all year. He induced grounders on 65 percent of balls in play off the curve, and hitters hit a paltry .267 on balls in play off the pitch.
That kind of weak contact helped make Koehler's curve one of the most valuable in the league. According to FanGraphs, his curve was the sixth-most valuable in the game overall. tied with Clayton Kershaw's infamous pitch. It is right alongside pitches like Felix Hernandez's, Jon Lester's, and Jered Weaver's this season. That is some high company for Koehler.
Overall, the season was a mild success. FanGraphs rated him as almost a two-win pitcher, while Baseball-Reference had him decidedly above that mark. Only Baseball Prospectus's Fair Run Average rated him poorly compared to the other two systems. Even if Koehler was just a 1.5-win starter for the team, it was a lot more than expected from a player who was thought to be on the way to losing his job by midseason. When the Marlins needed Koehler, he stayed healthy and performed.
Next year, the Fish have some decisions to make about their rotation, and Koehler again may be on the chopping block. But while he may succeed out of the pen eventually, he also proved he could put up solid back-of-the-rotation numbers for the Fish.