The continuing evolution of Jimmy Nelson

Like Wily Peralta before him, Milwaukee Brewers pitcher Jimmy Nelson arrived in the big leagues with expectations to fulfill. The 2010 2nd-round pick methodically ascended his way through the minor leagues and up top prospect lists, culminating in the #38 overall ranking by Baseball America in the 2014 Midseason edition of their Top-50 list. A sturdy build, mid-90s fastball, and sharp slider had fans and scouts alike dreaming of a durable and dependable presence near the front of a big league rotation.

Similarly to Peralta, however, Nelson still has yet to find the consistent success that was hoped for him when he debuted in the big leagues. Jimmy provided glimpses of what he could be during a solid 2015 season that saw him post a 4.11 ERA/4.10 FIP across 177.1 innings, but he could not carry that success over into last year. He fought his mechanics throughout the season while leading the league with 86 walks and 17 hit batters en route to a 4.62 ERA/5.12 FIP in 179.1 innings. He was particularly awful in the second half, authoring a 6.10 ERA during his final 14 starts of the season while issuing nearly five free passes per nine innings, allowing a .287 batting average against, and serving up 1.62 HR/9.

Nelson’s woeful finish to 2016 cast significant doubt on his future. He’s no longer young (he’ll turn 28 next month) and had seemingly regressed since arriving in the majors. It seemed likely that Nelson would be given one more chance out of spring training to try and stick in the starting rotation, but with young starters like Josh Hader, Brandon Woodruff, and Jorge Lopez knocking on the door for an opportunity, the leash would presumably become much shorter. With his fate as a Milwaukee Brewer hanging in the balance, Nelson needed to figure out a new approach to find success.

Through his first eight starts of the 2017 season, it appears as through Nelson has done just that. Coming into this season Jimmy had relied on his sinker as his primary pitch throughout his career, throwing it at roughly a 45% rate during his first three seasons. This year, however, Nelson has cut his sinker usage back significantly to just 30.2% while simultaneously increasing his four-seam fastball usage from about 23% during 2014-16 to 39.1% this season.

He’s also varying his location with the hard stuff from year’s past, as well. When pitching off of his sinker, Nelson stayed mostly to his arm-side within the strike zone, rarely utilizing the glove-side portion of the plate:

As he’s increased his four-seam fastball selection this season, Nelson has also increased his willingness to work to the glove-side part of the strike zone:

Jimmy has suffered from rather pronounced platoon issues since coming to the big leagues, as left-handed batters have touched him up for an .801 OPS during his career while righties have managed only a .701 OPS. Nelson had previously utilized his four-seamer just 24% of the time against lefties while relying on his sinker 45% of the time, which obviously didn’t produce the desired result. This year, however, Nelson has essentially flipped those selctions around and he’s now throwing four-seamers 44% of the time to lefties. He’s also been more comfortable throwing the new “split-change” that he was tinkering with during spring training, selecting it 9% of the time against left-handers (after previously throwing it less than 2% of the time during his career). The results have been palpable, as lefties are producing only a .680 OPS against Jimmy. The split-change in particular has held opponents to a .111 batting average against.

Besides getting lefties out more consistently, the biggest key to Nelson’s success this year has been limiting the traffic on the basepaths. Jimmy struggled to get ahead of batters last season and as a result, walked nearly 11% of the hitters that he faced. His stated mantra this year has been to fill the zone more consistently, and so far he’s done exactly that. His zone rate has increased by some four points up to 56.2%, leading hitters to take the bat off their shoulders more often instead of waiting for Nelson to walk them. While Nelson is generating more swings at his offerings, he’s also been generating more whiffs - his contact rate against is down by two points, his swinging-strike rate is much improved over last season, and he’s striking out a career-high 8.32 batters per nine. Nelson’s walk rate has plummeted to a manageable 7.9%, and he’s allowing hits at a lower rate this year than he did last year (8.9 H/9 versus 9.3 H/9) in spite his BABIP increasing from .299 to .315. After struggling to find a consistent release point throughout last season, Nelson has able to maintain a steady one this year, one that is lower than it ever has been before:

With Junior Guerra readying for a return from the disabled list before the end of this month, the Brewers will soon be faced with a decision regarding who to remove from the starting rotation. Jimmy Nelson is doing everything in his power to make sure that he doesn’t wind up being that guy. So far this year he has appeared to have refined his mechanics and changed his pitching strategy to address the shortcomings that have hampered him throughout his career, and the results have been thoroughly improved improved run prevention numbers. After last night’s start, Nelson now owns a 3.86 ERA/3.71 FIP through 44.1 innings this season. Jimmy Nelson doesn’t seem likely to become the frontline starter that some may have hoped for when he came up, but if he can sustain the improvements he’s made this season, he may finally be close to filling the role of a useful mid-rotation piece for the Milwaukee Nine.

Statistics courtesy of Fangraphs and Brooks Baseball