The Tigers’ 2018 starting rotation was better than you think

The Detroit Tigers’ starting pitching rotation showed improvement from 2017 to 2018 in some areas, while they regressed in others. Unlike the team’s league-worst batting lineup, their starting rotation ranked closer to the middle of the pack in most statistical categories. However, the difference may not mean a whole lot in terms of the future of the team.

This is so for two reasons. First, the Tigers traded away Mike Fiers, who was arguably their best starting pitcher, and there is no guarantee someone will replicate his production in 2019. Also, we can not be sure whether the team will build around the pitchers they have, or continue to trade away successful players while they wait for their top prospects to develop.

Whether the Tigers keep or trade Matthew Boyd, Michael Fulmer or Daniel Norris, they will need to pitch better. They will also need to pitch more often than they have thus far (Norris, in particular) if they are to be dealt for any prospects of note.

In any case, here is how the Tigers’ starters ranked among American league rotations.

The Tigers’ rotation cut down on the number of earned runs allowed in 2018, and brought their ERA ranking up to the middle of the pack in the American League. They also allowed significantly fewer walks and hits compared to 2017, which showed up in a reduced WHIP.

On the dark side, the Tigers gave up home runs at an increased rate of 1.53 homers per nine innings. This had a negative impact on their fielding independent pitching (FIP) and wins above replacement (WAR) numbers as a rotation. We don’t see the wide disparity between ERA and FIP that we saw in 2017. This can be attributed to a drop in their batting average allowed on balls in play (BABIP) from a league high .319 in 2017 to .285 this season, a drop of 34 points.

Considering that Detroit had the services of Justin Verlander for five months of the 2017 season, one could find a lower walk rate, lower batting average allowed, and a modest increase in strikeout rate in 2018 to be encouraging. However, they will have to do a much better job of keeping the ball in the yard before we can claim any real progress.

In terms of individual performances, we will compare the Tigers to all starting pitchers who threw at least 100 innings during the 2018 season. This gives us a group of 62 pitchers, or just over four starters per American League team.

It’s clear the Tigers lacked an ace in their rotation.

Verlander led the league with 6.8 fWAR, and the Cleveland Indians had four of the top nine starters in WAR this season. Detroit’s highest ranked starting pitcher was Matthew Boyd, who ranked 32nd at 2.0 WAR. Fiers ranked 38th, Fulmer was 40th, Jordan Zimmermann ranked 48th and Francisco Liriano was 58th of 62 pitchers.

Fiers turned in the lowest ERA in the Tigers’ rotation this season at 3.31, which was 10th in the league. The other four Tigers starters were significantly behind, grouped together between 38th and 45th, with ERAs from 4.39 to 4.69. Measured by FIP, all five Detroit starters fared no better than 38th of the 62 starters, with Fiers and Liriano having a large differential (in the wrong direction) between ERA and FIP.

Liriano posted the second-highest walk rate, and Zimmerman the third-highest home run rate among our group of 62 pitchers. Boyd and Fiers were the only Tigers to qualify for the ERA title with over 162 innings pitched, but this group of five Tigers starters accounted for 127 of the 162 starts this season. Daniel Norris made only eight starts, for a total of 36 innings with mostly unimpressive numbers. Chalk it up to another lost season. Blaine Hardy made 13 starts for 67 ²⁄₃ innings with decent numbers.

Perhaps the best news is that Liriano will be gone next season, to be replaced in the rotation by one of these left handers, or someone else.