Should Boston Red Sox set innings caps for Henry Owens, Eduardo Rodriguez?


It’s a debate that is raging throughout the baseball world as analytics increasingly becomes a factor in how franchises evaluate talent. How do you manage a young pitcher’s workload to balance their value to the team with preserving their arms for the future?

The Boston Red Sox find themselves in such as predicament with a pair of rookie pitchers as we head into the final stretch of the season. Henry Owens and Eduardo Rodriguez are expected to have bright futures as staples of this rotation, but with little left to play for in 2015, the Red Sox have started to ease their workload this month.

While each franchise has their own way of handling young pitchers, the Red Sox philosophy leans toward limiting their starters to a 20 percent innings increase early in their careers. Owens is rapidly approaching that threshold, while Rodriguez has already blown by it.

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Boston had hoped to manage the innings piling up on their young arms by moving to a six-man rotation, but that plan was blown up when Joe Kelly was ruled out for the season with a shoulder injury. Now the Red Sox can’t afford to shut down either of their rookie pitchers and will find it more difficult to give them extra rest between starts. As their inning totals continue to climb, the question facing the Red Sox is whether or not they need to be concerned about the number they are on pace to throw.

The problem with that question is that not all innings are created equal. A pitcher can breeze through an inning while throwing only 8 pitches or they can battle through a strenuous 30-pitch frame. The amount of stress put on the pitcher’s arm varies depending on how hard they had to work to get out of the inning, which makes innings caps an inexact science. What teams should be more concerned with is the number of pitches thrown.

Owens threw 159 innings in 2014 through stints in Double-A Portland and Triple-A Pawtucket. If the Red Sox were to stick to their 20 percent innings increase model then this would mean a target of about 190 innings this season, while he is currently up to 166 counting his time in Pawtucket and his 8 major league starts. Since Owens is averaging less than 6 innings per start in the majors, we can expect that he would be able to make his remaining three starts without surpassing that limit.

However, if we were to base his limits on pitch count then Owens may not have three full starts left in him. After throwing 2458 pitches last season, the Red Sox should be targeting approximately 2950 pitches if they were to allow a 20 percent increase. Since he is averaging a tick under 94 pitches per start in the majors with only about 197 pitches before hitting this artificial limit, that leaves him room for only two more full starts.

As for Rodriguez, he tossed only 120 innings in Double-A last season, so his target for innings would be 144. The lefty is already at 158 this season, so the Red Sox would have shut him down already if they intended to follow a strict innings cap.

Rodriguez did throw 145 innings in 2013, so if the Red Sox were basing his limits on his previous career-high then they could let him approach 174 innings. However, despite piling up more innings in 2013, he threw far fewer pitches than he did last year. Pitching primarily at the Single-A level, Rodriguez dominated the inferior competition that season, averaging a mere 11.7 pitches per inning to finish with a total of 1701 pitches. As the competition increased with a full-time jump to Double-A last year it became harder to grind through innings, resulting in his pitch count rising to 1955, despite lasting 25 fewer innings.

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Therefore any limitation set on Rodriguez should be based on a 20 percent increase of his career-high pitch count from last season, which puts his target at 2346. Since he has already thrown 2555 pitches this season, he has already exceeded this limit.

This data would lead us to believe that Owens should have at least two starts left in him, while Rodriguez should be shut down. Unfortunately it’s not as easy as looking strictly at the number of innings or pitches. The average number of pitches per inning matters too, as longer innings tend to be more stressful on a pitcher’s arm.

Owens averaged 15.5 P/IP in the minors last season, but that number has jumped to 16.5 this year. He has been far less efficient in the majors, posting a 17.2 P/IP through 8 starts. Only Kelly has averaged more pitches per inning on this Red Sox staff among those with at least 3 starts this season.

Rodriguez on the other hand has actually been more efficient this season, with his average dropping from 16.3 P/IP last year to 16.1 P/IP this season. A lower average suggests that Rodriguez has had fewer stressful innings, which means his pitch total may be less of a concern than it is for Owens.

There is no foolproof way to manage young pitchers. The Washington Nationals treated Stephen Strasburg with kid gloves in his debut season, but he got injured anyway and missed nearly the entire 2011 season. There have been plenty of other cases where pitchers have been worked harder, yet never broke down. Everyone is different and there’s no precise way to predict how a pitcher’s arm will react to the unnatural act of throwing a baseball. All teams can do is mitigate the risk by managing pitchers wisely with reasonable workloads.

With the Red Sox out of contention this season, there’s no reason for them to risk pushing their young pitchers. While being cautious is wise in this case, they must keep in mind that there are other factors beyond the number of innings pitched that should factor into this decision.