Tanner Roark is one of the more underrated starting pitchers in the Major Leagues. After a 2.85 ERA in nearly 200 innings in 2014, Roark was pulled from the starting rotation last year but has rediscovered his dominate stuff through 12 outings this season.
Even after Roark’s ugly start on Sunday when he surrendered 7 hits in a single inning, Roark still ranks 32nd in all of baseball (and 21st in the NL) in ERA with his 3.21 mark. What are the keys to his success?
First, his left-on-base % (a good indicator of coming improvements or regression because it is very difficult for a pitcher to be ‘skilled’ at leaving runners stranded) is lower than the league average (meaning that he has been unlucky in that regard) and his control has been pretty solid.
Tanner Roark’s K%-BB% (percentage of batters faced that Roark strikes out minus the percentage of batters faced that Roark walks) is the exact same (12.4%) as it was during his phenomenal 2014 season and while he actually is walking more than 3 batters per 9 innings, the huge uptick in Ks has really off-set that. Last season, the worst of Roark’s career, his K%-BB% was just 9.4% – as long as Roark can keep up the strong differential, Roark should continue to produce. Tanner Roark’s arsenal of pitches, the pitch velocity, and the rate at which he throws them have stayed relatively consistent over the past three seasons.
While a lot of Roark’s 2016 looks similar to 2014, there is a glaring change (and its actually a pretty good one). In 2014, only about 4 out of 10 batted balls off of a Roark pitch were hit on the ground, this leaves room for lots of fly balls which could inflate a pitcher’s home run numbers and a lot more extra base hits in general. This year, Roark is inducing a groundball more than 54% of the time and the results are clear. Not only are hitters making weak contact much more frequently (31% in 2016 vs 18% in 2014) but they’re rarely hitting for extra bases.
Through 12 2016 starts, Roark has allowed just 11 extra base hits (5 doubles, a triple, and 5 homers) which gives him an XBH/9IP stat of just 1.36. For comparison, Clayton Kershaw’s 2016 XBH/9IP is 1.46 during his historic start to the season and Tanner Roark’s 2014 XBH/9IP is almost a full extra base hit per game higher (2.31XBH/9IP).
As long as Roark continues to limit the extra bases (and I don’t see much reason why he can’t keep up what he’s doing), he will continue to be a valuable member of any starting rotation. Sunday’s rough start is likely more of an aberration than a new normal. He is not the same pitcher as he was back in 2014, he’s actually better.