One Big Question: Can Tyler Thornburg repeat his 2016 in the AL?

Welcome to Over The Monster’s One Big Question series. For the next 40 (week)days, we will be trying to answer one important question for each player on the Red Sox 40-man roster. The goal is to find one interesting portion of each player’s game to watch for, whether that be in spring training or the early regular season. We’ll be going straight down the list on the team’s roster page, meaning we’ll be going in alphabetical order through each position group, starting with the pitchers. Today, we’re highlighting Tyler Thornburg.

The Question: Can Tyler Thornburg build upon his breakout 2016 even after moving to the American League?

Most of you probably know that the Tyler Thornburg trade broke my heart because it sent Mauricio Dubon to the Brewers organization. Dubon was my favorite player at any level with the Red Sox, and even though it was a good trade it still hurt. This isn’t about Dubon, but I had to throw that spiel in there. No, this is about Thornburg, who was brought in to be Boston’s number two reliever behind Craig Kimbrel. That was the biggest consolation in all of this: Even though the Red Sox gave up Dubon (and Travis Shaw), they got an extremely talented reliever in return.

Once upon a time, Thornburg was a well-regarded starting pitching prospect who even made Baseball Prospectus’ top-101 list in 2013. He’s never really panned out in that role, though, and has made just 10 starts in his major-league career with his last one coming in 2013. As a reliever, he’s always had some potential but never really came through until this past season. And boy, did he come through.

Thornburg was one of the game’s best relievers in 2016, which was the righty’s first season surpassing the 30 game threshold at the major-league level. He threw a total of 67 innings over 67 games, and pitched to a 2.15 ERA, a 2.83 FIP and a 2.56 DRA. He also struck out over 12 batters per nine innings while walking a little over three. In other words, he was utterly dominant. Of course, this was his first season pitching like this, and he now has to deal with a whole new league that also happens to be the more difficult one for pitchers. Is he going to be able to make that transition?

The most worrisome part of Thornburg’s game as he looks to keep most of 2016’s gains is his home run prevention. This also relates to the transition to the American League, and it’s something he’s had issues with in the past. Just two years ago, he allowed seven homers in 34 innings. The 28-year-old is an extreme flyball pitcher, with his 36 percent ground ball rate finishing in the lower ten percent of the entire league. That can work out in terms of suppressing BABIP — look at guys like Marco Estrada and Chris Young — but it’s obviously a risk against power hitters and strong lineups.

The good news for Thornburg on this front is that he’s actually coming to a better home park for pitchers than Miller Park. The rest of the division will be a little tougher, similar to what I discussed with respect to Chris Sale except with the added difficulty of being a left-handed pitcher. On top of that, he’s going to be playing in front of a better outfield defense, and one of the elite trios in all of baseball. That won’t necessarily help with home run issues unless they can rob one, but it will at least play into his flyball tendencies.

Obviously, the biggest concern with a pitcher transitioning from the NL to the AL is that they are no longer protected by pitching to opposing pitchers. This isn’t really a big deal for Thornburg, though, who was a late-inning reliever. In fact, he didn’t face a single pitcher in 2016. That doesn’t mean he won’t be facing stronger lineups, though. He faced hitters in the ninth spot 22 times last year, and that was likely almost always a pinch hitter. It goes without saying that AL starters are better than NL pinch hitters on average. For someone who pitches in short stints like Thornburg, this shouldn’t have a huge effect, but it could be noticeable at times.

The important thing is that he has the weapons to succeed no matter who he’s facing. His strikeout rate was no accident, as he was in the top 16 percent of pitchers in terms of swinging strike rate. The key to everything were his two primary pitches: The fastball and the curveball.

His fastball was the most noticeable change he made heading into 2016, as he ramped up his velocity up to 95 mph. While he’s been a reliever for most of his major-league career, he remained stretch out by starting in Triple-A prior to last season. In 2016, he was able to let loose and focus entirely on short stints, and it showed with the heater. The pitch generated whiffs on nearly a quarter of swings it induced.

The curveball, meanwhile, took the step into being a dominant secondary he could lean on. He threw the breaking ball about a quarter of the time, and at just 80 mph with movement it was a perfect compliment to his newly charged fastball. The pitch generated whiffs on more than 43 percent of swings, and induced ground balls on half of balls in play. Just look at the curve Thornburg throws to Kris Bryant here.

In the end, there are more positive signs for Thornburg as we look ahead to 2017 than negative ones. He may only have one great year under his belt, but there are indicators like his improved fastball that he made real changes. Any time a pitcher transitions from the NL to the AL is scary, but it’s not as big of a deal for someone who comes from a hitter-friendly park and pitched in the late innings. Home runs might be a bigger problem with his flyball tendencies and slightly stronger lineups, but everything else should make up for that. As long as he doesn’t become a total launching pad, Thornburg should remain a reliable number two to Kimbrel.