Milwaukee Brewers: What Happened to Mike Fiers’ Fastball?

Mike Fiers is somewhat of an anomaly in baseball. A 22nd round draft pick by the Brewers in 2009 at age 24, Fiers achieved remarkable success during his climb through the minor leagues while relying on less-than-dominant “stuff” to produce consistently dominant results. The Florida native made his big league debut in 2012 and was shuttled back and forth between the minors and majors until last season. After being called up for four relief appearances in June of 2014, Fiers was back in the bigs that August, replacing an injured Matt Garza in the starting rotation and making 10 stellar starts through the end of the season.

All-in-all last season, Mike produced a 2.13 ERA in 71.2 major league innings, striking out 76 batters while walking just 17 with a WHIP of just 0.88. Fiers’ Deserved Run Average (DRA) was a miniscule 2.70, or 34% better than MLB average. His cFIP- of 80 ranked 23rd best among the 208 pitchers that threw 70+ innings last year, and his DRA_PWARP (Baseball Prospectus’s version of Wins Above Replacement) of 1.81 ranked 65th though he appeared in just 14 games.

The key to Fiers’ success in 2014 was his ability to dominate hitters with his fastball. Though he throws the pitch at an average velocity under 90 MPH, Mike’s fastball was valued at 17.8 runs better than average last season; his wFA of 17.8 ranked him third in all of baseball despite ranking 197th in innings pitched. Pertinent to Fiers’ success has been his deception and location. Utilizing a changeup and slow curveball as his primary off speed pitches, Mike most often throws these two pitches down-and-in to right handed hitters, setting up for his fastball high in the zone. Mike threw nearly a quarter of his fastballs up-and-in to righties in 2014, almost avoiding the bottom of the zone altogether. 51 of his 76 strikeouts came via the fastball and he allowed just a .127 batting average against and .255 slugging percentage against his four seamer.

Mike Fiers 2014 fastball heat map, courtesy of BrooksBaseball.Net.

This season, however, Fiers’ fastball usage has been dramatically different. While he still utilizes his off-speed pitches low-and-inside, he has greatly reduced the amount of fastballs he is throwing up in the strike zone. Mike threw only 9.71% of his four seamers to the bottom fifth of the zone last season, but that number is up to a whooping 37.13% percent this season. In 2014, Fiers used his fastball as his most dominant “put-away” pitch; he threw it 63% of the time he had a two-strike count to a right handed batter and 62% of the time to a left-handed batter. This season those numbers are down to 56% of two-strike counts to righties and 52% against lefties, while his curveball and changeup have both seen increases in usage as two-strike pitches. Fiers has recorded just shy of 57% of his strikeouts via the fastball this year, a decrease of more than 10% from last year. Mike is currently sporting hefty a .294 batting average against his fastball with a whopping .497 slugging percentage against, and his wFA of -4.4 this year ranks 13th worst in the MLB.

Mike Fiers 2015 fastball heat map, per BrooksBaseball.Net.

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With his new approach, Fiers has stumbled through a mountain of inconsistency this season. Though he has seen a slight increase in ground balls (now up to 38.5%) and K/9 (9.62), he is also walking 1.28 more batters per nine (3.41 this season) and has nearly doubled his WHIP (1.47) since his 2014 campaign. Fiers is giving up the most hard contact in the majors by more that 3% this season (and 39.6% of the time), so we shouldn’t be altogether surprised by his rather high BABIP of .349 (batting average on balls in play, league average is typically around .300). The home run ball has stung Fiers more this year than last; he’s seen increases in both his HR/9 and HR/FB ratio, and 7 of his 10 home runs given up have come off the fastball. In 87 innings pitched so far in 2015, the 30 year old right hander has posted a 4.14 ERA, six percent worse than league average, and a DRA of 4.38, five percent worse than league average. Fiers’ DRA_PWARP of 0.55 ranks him as the 163rd most valuable pitcher in the major leagues this year.

The silver lining for Fiers could be that with a cFIP- of 89, he is predicted to be solidly above-average going forward. He has looked much better over his last two starts: 13 IP, 3 earned runs (one home run), 11 strikeouts, and a WHIP of 1.00. Fiers focused almost solely on the lowest fifth of the zone during that time, perhaps suggesting that he is becoming more accustomed to this new method for attacking hitters. It is fair to question what precipitated this dramatic change in approach, but as the season marches on, it will be interesting to see if Fiers can discover the same success he experienced last season while abandoning his once dominant high fastball.

Next: NL Central Week 12 Power Rankings