How Wes Johnson has turned around Twins pitching

Coming into the 2019 season, many surmised that the Twins offense would be one of the better units in the league. The front office invested in the lineup, picking up four batters that are everyday players for the Twins. The pitching situation was a different story, as the Twins inked just Martin Perez and Blake Parker, both on cost-friendly deals.

Another pickup pertaining to the Twins pitching was a new coach, Wes Johnson. While fans and media wondered if the Twins would invest more in the bullpen or starting rotation, the front office seemed to believe that the new pitching coaches - Johnson and data-driven bullpen coach Jeremy Heffner - could make significant improvement to the staff as it was.

Much like the signing of Perez, staffing Johnson as the pitching coach was a unique move. Not often do coaches jump from college ranks to a prominent position on an MLB, in fact this article states that he is the only pitching coach to come straight from a position on a college team. Johnson was able to mold collegiate pitchers into pros, helping 30 college pitchers get drafted in his time as a college coach. He also was known for increasing velocity in his staff and studying biomechanics and analytics, which is believed to be contrary to the philosophy of previous regimes.

Johnson is more than familiar with the new tools to evaluate pitching at the big league level, and used some of them before they were even purchased by MLB teams. The former college coach got his hands on a Trackman system when coaching at Dallas Baptist and also started applying a significant doses of biomechanics into his coaching nearly a decade ago. While not as many technical tweaks can be made at the Major League level, it seems that Johnson’s presence has been felt so far for the Twins.

Looking at the pitch repertoire for the team, it appears that Johnson’s influence is changing how the Twins attack batters. After ranking fourth in the MLB in fastball percentage last year (throwing in 59.1% of the time) they rank 20th in heaters thrown at 51.9% in 2019. They have also increased their average velocity on their fastball as a team, as the pitch has become more effective for Twins pitchers. The Twins are also featuring more curveballs, throwing the pitch 15.1% of the time compared to 12.4% last season.

As a results, contact on pitches both inside and outside the zone for opposing batters is down compared to last season (contact in the zone has dropped over two percent). The Twins are also throwing more first pitch strikes (62.8% to 58.5%) and opponents are swinging and missing more frequently in 2019 as well.

As a team, their strikeout to walk ratio has improved from 2.4 to 2.8 (a significant jump for a team statistic) and their team ERA is up to seventh in the MLB at 3.80 (last year they finished at 4.50). Their xwOBA (expected weighted on-base percentage) against ranks tenth in the MLB at .314, a sizeable improvement from their 2018 mark of .327.

How much of this improvement comes from Johnson’s adjustments and coaching? While one can merely guess at the answer to that question, it is interesting to look at a few factors that may have aided those team improvements on an individual level. First I took a look at fastball velocity from last season to this year to see if there was a significant increase in speed for more than just Martin Perez. (none of the graphs below feature Michael Pineda or Ryne Harper, as they didn’t pitch last season)

The results were mostly positive, with the biggest differences coming from Perez and then Odorizzi, who have both exceeded expectations. May and Rogers’ uptick in velocity is also encouraging, especially as they are counted on to get outs in high leverage situations as the Twins attempt a run at the playoffs.

On a side note, the drops in velocity aren’t too concerning. Berrios seems to be savvy enough to mix and match fastball speeds, and he also had a couple starts when it was a bit colder where his velocity was down. Hildenberger doesn’t rely on his fastball much, and Gibson’s results are likely a bit skewed after losing 20 pounds prior to the season with e. coli.

Whiff percentages are also encouraging when looking at the numbers from last season. Perez takes the cake once again as the most improved, with Odorizzi following close behind. Gibson is in the third spot with his impressive 11 strikeouts performance against the Blue Jays.

The steep drop off in whiff percentage for May is curious, though his other Statcast numbers suggest that he is doing just fine. He currently ranks 1st in the MLB in average exit velocity against (79.5 MPH) among pitchers who have had more than 30 balls put in play when they are on the bump. Once he regains complete control of his curveball, I expect his whiff rate to return closer to last year’s mark.

This graph shows that there haven’t really been too many jumps in xwOBA against from the Twins pitchers, with two positive leaps (you guessed it, Perez and Odorizzi) and one steep drop off (the injured Mejia).

So what does all of this tell us about Wes Johnson and the Twins pitching staff? Though the sample size is still small and the reason behind the results isn’t always clear, it appears that the new pitching regime has had a significant effect on Odorizzi and Perez while having nominal (but trending more towards positive) effects on the rest of the staff.

Some of these statistics could change with an disastrous outing or a week of dominant appearances, but early results show that the Twins decision to employ Johnson as the new pitching coach has paid dividends.