5 MLB Pitchers Who Have Taken a Huge Step Forward in 2017

Patrick Corbin, SP, Arizona Diamondbacks

To say Patrick Corbin's big league career has been a bumpy ride is probably quite the understatement. The Arizona Diamondbacks southpaw appeared to be a budding star in 2013 -- he not only threw 208.1 innings as a 23-year-old, but also added 14 wins to go with a 3.41 ERA and 3.5 fWAR in an All-Star campaign.

But then, it happened. And by "it", we're talking about Corbin needing to go under the knife for Tommy John surgery.

In his first full season since the procedure, the lefty went just 5-13 through 155.2 innings with a 5.15 ERA in 2016, and even found himself demoted from the rotation to the bullpen in order to work things out. His 4.38 SIERA showed he was a bit unlucky, but with single-season career worsts in strikeout rate (18.7%), walk rate (9.4%), and hard-hit rate allowed (38.5%), he clearly had some work to do if he wanted to regain that All-Star form.

In nearly the same number of innings this season (152), Corbin has returned to being a productive starter for Arizona, as he's gone 11-11 with a 4.09 ERA during that time. While he's still allowing more home runs than he did earlier in his career (1.36 per nine innings), his ground-ball rate is on track to be above 50.0% for the second consecutive season. Also, his SIERA (3.98), strikeout rate (21.8%), walk rate (6.4%), and hard-hit rate allowed (31.9%) are much more in line with what he's done in the past.

This resurgence can be attributed to a shift in pitch usage -- he's throwing his fastball just 53.0% of the time, which is 10 percentage points below his career average. That difference has gone directly to his slider, which he's throwing 36.9% of the time. He's produced a 23.9% swinging-strike rate with that pitch, which is the only one in his arsenal that's generated a whiff rate higher than 7.6% this year.