What exactly is Mike Fiers?

The Brewers’ Mike Fiers is having an odd start to the 2015 season. Seven starts into the year, the 29-year old RHP is somehow sporting both an unsightly 5.00 ERA and a 12.3 strikeouts per nine rate, two figures which have received some note of late. Combine the highest K/9 in baseball with his 89.4 mph average fastball velocity, and it’s a fairly unusual line. To what can these numbers be attributed?

First, it should be noted that the more popular ‘K/9’ metric is a little misleading here – Fiers does strike out a lot of batters, but ‘per nine’ stats divide by the number of outs made. With his ERA, it should be plain that a lot of his plate appearances end with runners reaching base. Using the more representative strikeout percentage (strikeouts / plate appearances), he is still very strong but only 4^th best among qualified starters.

FIP also is a fan of Fiers, relatively speaking, with over a run of difference between it and his ERA. His high HR/FB rate is seen in his even lower 3.31 xFIP. A problem, though, is that Fiers’ home run problem might not be a fluke.

*DRA is a new run estimator from Baseball Prospectus

Fiers has also walked a fair amount of hitters, but it is far from his biggest problem - that looks to be his batted ball profile. As a pitcher who works predominantly off a four-seam fastball, Fiers has never generated a large number of ground balls, and this season many of those fly balls are becoming home runs.

A 15.0 percent HR/FB rate is high enough that regression might be expected. However, using Fangraphs’ quality of contact metric, his sky-high 48 percent hard-hit contact rate is troubling (league average this season is 28.6 percent). That rate is a career worst for Fiers, who is also throwing strikes at a lower rate than his prior career average (64.9 percent).

In terms of opposing batters’ discipline, Fiers is mostly in line with league averages. One notable exception is on out-of-zone contact, where he is 6.5 percentage points better than average. He is fooling a decent number of batters on outside offerings, likely resulting in some of his strikeouts. Which offerings might those be?

Mike Fiers is among the leaders in the percentage use of four-seam fastballs (55.8 percent) among starters, and almost evenly divides the remainder of his pitches among his change-up (14.9 percent), curveball (14.3 percent), and cutter (14.0 percent). Looking at opposing batters’ production per pitch, potentially ineffective pitches can be identified.

To this point in the season, batters have feasted on Fiers’ hard offerings while struggling against his secondary pitches. All six of his home runs allowed, as well as the majority of the high fly ball rate, have come off either the four seam or the cutter. In particular, he has failed to induce many swings and misses or strikeouts with the cutter.

On the other hand, the three other pitches each produce well above average numbers of swings and misses, with the changeup and curveball producing strong ground ball, walk, and wRC+ rates. How about the quality of the pitches themselves?

The first thing that is apparent is the velocity of Fiers’ pitches. While the changeup is almost spot on league average, the hard pitches are each about 2 MPH slower than average, while his looping curve is about 5 MPH slower.

The 2 MPH drop not applying to the changeup means a smaller differential from the fastball, typically a bad thing. However, Fiers averages over 6 inches greater horizontal movement on the pitch than the average, resulting in weak contact and some whiffs.

His cutter exhibits almost exactly league average movement in both planes and has been Fiers’ weakest offering to this point. The curve has been the best offering, seeing only 14.3 percent fly balls with an astounding 55.6 percent strikeout rate. It sees 6.5 inches greater vertical movement than the average curve ball; hitters rarely swing at it, even in the zone, and rarely ever make contact on the pitch.

The four-seam fastball is fairly flat, causing many of Fiers’ problems, but also results in a high percentage of strikeouts. Using it such a high percentage of the time, it makes sense that he sees both a large number of strikeouts and gets hurt often when hitters do connect.

Fiers clearly targets down and glove-side for both his curve and cutter while targeting arm-side and mostly down on his changeup. His four-seam fastball is all over the strike zone, and a look at his slugging percentage zones shows that the ones left up are predictably the ones that cause the most problems.

This leads me to believe that the key to Fiers' success is simply hitting his spots. At his best, like when he struck out 12 Cubs in six innings on May 2nd, Martin Maldonado didn’t move his glove an inch to receive the ball. The fastball doesn’t have any strong movement or the velocity to blow away a hitter, but when placed properly generates plenty of swings and misses.

On the other end of the spectrum, watch Alex Guerrero murder a fastball left in the middle of the plate and note how far the catcher set up on the edge. Or watch Ryan Zimmerman doing the same thing to a ball missed in the same spot several months earlier. Or watch Jay Bruce and Todd Frazier hit grand slams in back-to-back innings on a four-seam fastball and cutter, respectively, both missing right over the middle of the plate.

Mike Fiers is an exciting pitcher when he’s on target. This seems to be an example of having fastball control but not consistent fastball command. He throws the pitch for an above average number of strikes, getting punch-outs, but has a tendency to miss within the strike zone, getting punished for it. His secondary pitches are very good pitches, and it would be interesting to see Fiers use them a higher percentage of the time if he continues to struggle with intermittent fastball command.

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Spencer Bingol is a Contributor at Beyond the Box Score. You can follow him on Twitter at @SpencerBingol.