The Detroit Tigers featured a historically good starting pitching rotation during the 2013 season, setting an all-time record for strikeouts while leading the league in rotation ERA, home run rate, and blowing away the league in fielding independent pitching (FIP) and fWAR. The 2014 starting rotation has not fared as well, but the numbers show that the Tigers’ starting pitchers are as good or better than any in the American League.
|Category||2013||2013 AL Rank||2014||2014 AL Rank|
As you can see, the 2014 Tigers’ rotation led the league in several categories while their strikeout rate dropped and the team’s FIP and ERA rose over their 2013 numbers. This comparison provides an indication of just how historically good the Tigers rotation was in 2013.
They set the bar higher than any team's rotation could reach in 2014, and set expectations higher than the 2014 Tigers’ rotation could achieve. The Tigers' full-time starters ranked 1st, 2nd, 4th, 8th, and 22nd in the league in WAR in 2013. The 2014 cast ranked 3rd, 6th, 15th, 18th, and 20th. Clearly not as good, but all five pitchers rank among the top 20 starters in the American League. That's still an amazing rotation.
When compared with the other teams in the AL, we can see that the 2014 Tigers’ starting rotation led the league in home run rate, home run to fly ball ratio, innings pitched, wins, and fWAR. They ranked second in FIP, second in walks per nine innings, and fifth in strikeouts per nine innings.
What stands out is that the Tigers’ rotation ranked 10th in the league in rotation ERA, but second in FIP. The difference between FIP and ERA can be attributed to a few main factors. One is random variation, but here we have over 1,000 innings pitched, so the luck of where a ball is hit should not be a factor in this case. Another possible factor is that a team could be giving up harder contact to hitters, resulting in more hits instead of outs. The fact that the Tigers had the lowest home run ratio in the league points in the opposite direction.
The other big factor is defense, and this does make a huge difference with the 2014 Tigers. The difference is 0.51 runs per game in this case. That is enough to drop Detroit from second in FIP to tenth in ERA. Defense plays a part in helping some teams while hurting others when you attempt to use ERA to measure the performance of a pitcher, or a team’s rotation or bullpen as a group. As a percentage, 0.51 runs attributable to defense out of 4.29 runs allowed is 13 percent. The other 87 percent is attributable to pitching.
One significant area where the rotation declined in performance from their banner year in 2013 is in the strikeout ratio, which is down almost one strikeout per nine innings. Strikeouts are the surest way to avoid reliance upon a weak defense, which, as we described in the defensive report card here, ranked below average in seven of the eight positions when a ball is put into play. Every strikeout essentially avoids a 31 percent chance of a base hit.
Even more striking is the second half differential between ERA and FIP. While the Tigers’ ERA rose from 3.84 in the first half to 3.95 after the All-Star break, their FIP dropped from 3.69 to 2.98 in the second half. This opened a gap of nearly a full run per nine innings in the second half of the season between ERA and FIP. The Tigers strikeout rate in the second half was back up to 8.32 per nine innings (second in the league) and their walk rate and home run rate were even lower. The result was a sparkling FIP.
One other factor in the numbers is the impact of the bullpen on ERA. I don’t believe this was a huge factor in 2014 for a few reasons. For one, Detroit relief pitchers allowed 80 inherited runners to score. That is ten runs above the league average, and 32 percent is second highest in the league. While these runs show up in the previous pitcher’s ERA, they comprise two percent of the total runs charged to the starting pitchers. Two, an inherited runner is a shared responsibility, unlike the case where a runner reaches base due to poor defense. So the Tigers bullpen did have a negative impact on the team’s rotation ERA, but not a large impact.
The 2013 Tigers didn’t have a great defense, either, but the starting rotation had such a wide lead over the next best rotation, that they were still able to post the best ERA in the league. Not the case in 2014. The Tigers rotation were mere mortals in 2014. By comparison with the 2013 rotation, their performance was down significantly. By comparison with the rest of the league, they were as good or better than any other rotation.
What grade do we give the 2014 Tigers’ starting rotation? I’m giving them an A-.