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One Big Question: Can Tyler Thornburg keep his stuff after undergoing TOS surgery?

It would be a huge boost to the bullpen if he could.

Boston Red Sox Photo Day Photo by Elsa/Getty Images

Welcome back to the One Big Question series here at Over The Monster. For those who weren’t around for last year’s series or simply forgot what it entails — there’s a lot going on in the world today, so don’t be ashamed! — here’s a brief reminder. Every day, Monday through Friday, for the next eight weeks we’ll profile a new member of Red Sox 40-man roster. Rather than simply going through a simple profile of their overall game and what they offer the team, we’ll focus on the one question that could very well dictate how their season will go in 2018. In order to keep the order objective and avoid side conversations like ranking the players on the roster, we’ll go straight down the roster in alphabetical order by position. In other words, we’ll go by how things are ordered here. If you miss any editions or would like to look back on some of last year’s, you can see all of them here. Today, we’re looking at Tyler Thornburg.

The Question: As he returns from TOS surgery, can Tyler Thornburg regain the stuff that made him so great in 2016?

I’ve talked about the Red Sox bullpen a whole lot recently, and there has been one overwhelming theme that you are surely sick of hearing about by now. That is that there is a ton of upside with this group (and we saw them hit that upside in 2017) but also plenty of downside. There is only one guy who is close to a sure thing (Craig Kimbrel) and everyone else has a wide range of possibilities. Where on the spectrum of possible outcomes each pitcher falls will play a major role in how the season works out for the Red Sox, even with a presumably improved offense that should work to keep some of 2017’s pressure off the relief corps. I talked yesterday, in this very series, about how Carson Smith is arguably the most important question mark on the roster, and I stand by that. However, Tyler Thornburg may be the biggest question mark and could be the biggest boost from expected to actual value.

Pittsburgh Pirates v Milwaukee Brewers Photo by Stacy Revere/Getty Images

Thornburg, of course, was acquired last winter on the same day the team traded for Chris Sale. The right-handed reliever came over from Milwaukee in exchange for a package that included Travis Shaw, Mauricio Dubon and Josh Pennington. Thornburg then proceeded to go down with shoulder trouble in spring training and is yet to make his Red Sox debut. After an effort to rehab the ailment, he underwent surgery for Thoracic Outlet Syndrome in June that ended his chance of pitching in 2017. This is not as high-profile a surgery as Tommy John, of course, but it seems to be more common of late (or maybe I’m simply just noticing it more) and the return is as treacherous as Tommy John once was. As he continues to work his way back and hopes to make an impact on the 2018 season, it’s fair to wonder whether or not he’ll get his stuff all the way, or even most of the way, back.

Make not mistake, either. Thornburg getting his stuff back is essential for his success in the major leagues, as it’s the biggest reason why he was so successful in that 2016 season. It can be easy to forget now that he’s missed an entire season and Travis Shaw put together a really strong year in Milwaukee in 2017, but Thornburg was phenomenal in his first full season as a reliever in 2016. Over 67 innings and 67 appearances, the righty finished with a 2.15 ERA with a 2.86 FIP and a 2.69 DRA (40 percent better than the league-average pitcher). There were certainly some command issues as he walked about 3.5 batters per nine innings and allowed a respectable, though not great, seven home runs, but his ability to miss bats wiped away any concern. Thornburg ended the season with over 12 strikeouts per nine innings and increased his swinging strike rate by seven percentage points (from 21 percent to 28 percent) over the previous season.

Obviously, the stuff Thornburg has in his repertoire is what led to the strikeouts, and the Red Sox are really hoping he can maintain the same quality of arsenal after coming back from his surgery. A former starter, Thornburg does have three pitches to which he can turn, but he’s mostly scrapped his changeup in his conversion to full-time relief. Now, he’s a fastball/curveball pitcher with a mid-to-high-90s fastball that generated whiffs on a quarter of swings and a big, slow breaking ball that generated whiffs on 43 percent of swings. The curve also induced grounders on exactly half of the balls in play against the pitch, for what it’s worth. It was a deadly arsenal and when he was going right he could throw either pitch at any time with extreme confidence.

Unfortunately, the road back from TOS surgery has proven difficult for every pitcher to come back from, particularly right away. Matt Harvey is perhaps the most high-profile case of this, and he’s watched his strikeout rate fall from around a batter per inning in 2015 to just 6.5 per nine in 2017. We’ve also seen this type of drop off from guys like Tyson Ross and Jaime Garcia, too. It’s important to note that there are successful comebacks from TOS surgery — Garcia is one of them, in fact, though he did struggle a bit with strikeouts immediately upon his return — but the track record is mixed at best and a cause for pessimism at worse. It’s also worth noting that pitchers coming back from this have struggled with control and command in addition to strikeouts. However, at his peak Thornburg can mask some control/command issues because his fastball/curveball combination proved to be so dominant when it’s working correctly.

At this point, with Thornburg still throwing off flat ground and having no basis on which to base expectations for the now-29-year-old, the safe course of action is to expect little from Thornburg. The righty has the talent to be a legitimate back-of-the-bullpen arm, and he’s proven that at the major-league level. We just don’t know if he’ll get that stuff back. The Red Sox are going to work with him to get it back, of course, and they’d be wise to take their time and value the quality of his stuff when he returns over the percentage of the season in which he can pitch. If Thornburg does get his stuff back for 2018, though, it is the biggest potential boost we could see for this Red Sox roster.