Over at Baseball Prospectus, Russell Carleton assembled a list of factors that predict pitcher injuries. He doesn’t release any of his regression equations (probably out of fear of them being misused), but he does give percentages for injuries and DL trips based on past instances. Best I can tell, his work treats all injuries as being equal which obviously isn’t true to reality. Nonetheless, he sheds some light on which injuries would be likely to resurface and alerts us to some potential warning signs.
His most frightening finding was that players who sustained any sort of injury one season had a 73.4% chance of getting hurt the next year. This is very bad news for the Yankees. Outside of Hiroki Kuroda and David Phelps, everyone projected to make the Yankees rotation and bullpen missed time with some sort of injury last season. For DL trips, a player had a 43.7% chance of ending up on the DL if he was there last year. This is really bad news for the starting rotation. CC Sabathia, Andy Pettitte, and Ivan Nova all spent time on the DL last year.
Carleton also points out factors that tend to predict shoulder and elbow injuries. Outside of past injury, pitches thrown and a decrease in batters faced tend to indicate higher probability of shoulder injuries. The potential red flags here are Kuroda and Hughes who both threw over 3200 pitches and Sabathia who faced 152 fewer batters in 2012 than in 2011.
As far as elbow injuries go, the leading predictor is a low HR/BF in the prior season. This matters even more than past injury history. My best guess is that this acts as a proxy for guys who throw a lot of breaking balls which can put a strain on the elbow. Sabathia, Kuroda, and Pettitte all had HR/BF below the league average is especially significant considering they pitch half their games in Yankee Stadium. Drops in batters faced and innings also put pitchers at risk (Sabathia). A high ERA is also a risk factor (Nova).
Keep in mind that this model isn’t perfect and we shouldn’t simply assume someone will get injured if they meet a certain criteria. Nonetheless, it is alarming to see Sabathia’s name show up as often as it has. His time on the DL last year, drop in batters faced, low HR rates, and even pitches thrown (3028) makes him a risk no matter how way you slice it. Specifically, his elbow seems to be at risk: Low HR/BF? Check. Elbow injury last year? Check. Drop in BF and IP? Check. He’s also coming off of an elbow surgery which is certainly a factor. However, it’s not clear if that’s a good or bad thing. Did the surgery “fix” his elbow and eliminate these risks? Or does he have a greater risk of recurrence now?
Looking beyond Sabathia, most of the rotation is has red flags simply because they spent time on the DL last season. Here’s a back-of-the-envelope calculation:
According to Baseball Heat Maps, the average DL trip last season for a pitcher lasted about 61 days. 43.7% x 61 x 3 pitchers (Sabathia, Pettitte, Nova) = an expected DL total of 86 days. Hughes would have a 24.4% chance of a DL trip thanks to his time spent there in 2011. If we assume a 3.5% chance (the percentage associated with 2 years of being healthy) for Kuroda and Phelps, we get up to 105 days on the DL among the 6 Yankees’ starters. The MLB regular season is only 182 days so we’re looking at over half of one season spent on the DL. This doesn’t sound too bad until you consider that injuries don’t happen one at a time. It’s very likely that 2 or more starters will be on the shelf simultaneously. To make matters worse, I didn’t even account for the day-to-day injuries that always pop up. According to Carleton’s numbers, these guys are highly prone to injuries in general due to their injuries last season.
Having injury-prone pitchers wouldn’t be as much of an issue if the Yankees had any sort of rotation depth. After the front 6 (excluding the injured Michael Pineda), there’s a significant drop-off to Adam Warren. After that, there’s not a single starter who ended 2012 in AAA. The options would be: Brett Marshall, Dellin Betances, Vidal Nuno, and Shaeffer Hall. Warren’s probably a replacement-level starter at this point while everyone else is still at least a few ticks below replacement. Quite frankly, this is puzzling. They’re going to need to use their 7th and 8th starters at some point and it’s a mystery to me why don’t have a veteran or 2 in camp to stash in AAA. Hopefully, these starting pitchers prove the numbers wrong and stay relatively healthy. If the injury bug does bite though, things could get ugly in a hurry given the team’s lack of starting pitching depth.
Photo by Keith Allison [CC-BY-SA-2.0], via Wikimedia Commons