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

Jimmy Nelson, SP, Milwaukee Brewers

A major concern with Milwaukee Brewers right-hander Jimmy Nelson over the years was his general lack of control. Between 2014 and 2016, his walk rate steadily climbed (6.1%, 8.6%, 10.7%), as did his SIERA (3.76, 4.09, 4.92). It also didn't help that his strikeout rate basically stagnated under 20.0%.

One of the big reasons why the Brewers are still in the hunt is because Nelson made these concerns a thing of the past with a true breakout campaign. His 4.3 fWAR is only behind Max Scherzer among qualified NL pitchers, and his 3.44 SIERA, 26.7% strikeout rate, and 11.3% swinging-strike rate are all on track to be career bests.

There's an old saying that "The best pitch in baseball is strike one." Nelson has taken that to heart -- his current 62.4% first-strike rate is the highest it's been since 2014 (62.7%), and it's on pace to finally get better instead of steadily declining in both 2015 and 2016.

Nelson has also significantly increased the usage of his curveball compared to last year (12.4% in '16, 18.5% so far in '17), and it's become his best pitch, according to Pitchf/x. He allowed walks 12.3% of the time with this pitch in 2016, but has cut that all the way down to 2.1%. Meanwhile, his strikeout rate in this situation has gone from 27.6% to 41.1%.

So that explains why his wOBA allowed on curveballs has decreased from .348 in 2016 to .205 in 2017.