PITCHf/x Forensics: Zach Britton

Per Baltimore Orioles: Zach Britton on 10-day DL w left forearm strain. RHP Stefan Crichton recalled from Triple-A Norfolk. (cc: #BlueJays)

— Laura Armstrong (@lauraarmy) April 16, 2017

Hot off the press, the world’s best relief pitcher has been sent to the Disabled List with a dreaded forearm strain. A strain, for those of you not familiar, is the tearing of a muscle or a tendon. This is a big deal in the forearm, particularly for a pitcher, because these muscles are the ones that protect the UCL during the pitching motion.

We are all familiar with the performance Zach Britton put out in the 2016 season – arguably, one of the most dominant relief pitching performances of all time. What was happening under the hood to lead to this injury?

I have broken this analysis down by the 6 predictors discovered by Whiteside et al., (2016): Shorter stature, high velocity, high pitch counts per game, less pronounced horizontal release point, less time between game appearances, and fewer pitches in the repertoire. I also looked at the predictors for injury that I developed on this site – the amount of variability in Stuff, and high workloads measured by Fatigue Units. In this table, the values in the top section represent high, moderate, and low levels of risk based on these variables, and the colours of the values next to the pitcher’s name represent which risk level that pitcher falls in to. Green is low risk, yellow is moderate, and red is high. Let’s look at Britton, here.

In 2016, Britton pitched 19 times on consecutive days, resulting in a very low, average days between appearances of 2.66 days. This falls into the high risk category. His high velocity, horizontal release point are also in the high risk range. Of particular interest, Britton only had one pitch that he threw greater than 10% of the time – that otherworldly sinker. He has a very low pitch per game level – a testament to his ability to get strikeouts early, and induce ground balls. Interesting to note, while he has racked up the saves against the Toronto Blue Jays this season (and who hasn’t??), the Jays found a way to push Britton to his limit without breaking. In 2016, he threw an average of 14.88 pitches per outing. In the past two games he pitched against the Jays, throwing 18 and 21 pitches.

With respect to his workload in 2016, he had a moderately high workload, of 15.37 Fatigue Units, and a very low fatigue units per game value – so no blindingly evident risk factors popping up there. His stuff variability also fell into the moderate range, so the Sonne predictors aren’t saying too much to point towards a cause of injury here.

With respect to the timelines for Britton to return – this is a tricky one. This type of injury can represent a “where there’s smoke, there’s fire”, type of thing. Rushing Britton back before the muscle is completely healed would jeopardize the integrity of his elbow during throwing, and if he wasn’t at risk of a UCL tear before, he would be then. On the flip side, if this is a mild strain, Britton could return right after his time on the 10 Day DL.

This is something to keep a very close eye on as the season progresses.

References

Whiteside, D., Martini, D. N., Lepley, A. S., Zernicke, R. F., & Goulet, G. C. (2016). Predictors of Ulnar Collateral Ligament Reconstruction in Major League Baseball Pitchers. The American journal of sports medicine, 0363546516643812.