Thornburg, a late-inning reliever identified by the Red Sox as a key offseason addition in a trade with the Milwaukee Brewers, will undergo surgery to treat thoracic outlet syndrome in his right (throwing) shoulder, the team announced Thursday. The procedure will be performed on Friday by Dr. Robert Thompson at Barnes-Jewish Hospital in St. Louis.
The Red Sox expect Thornburg to be ready to pitch next season.
"It's a very unfortunate situation for him," Red Sox president of baseball operations Dave Dombrowski told reporters Thursday in Philadelphia. "But I think it's also a relief that somebody has finally been able to come to the conclusion of what his problems have been."
The Sox have been vague about Thornburg's status since he was shut down in late February with shoulder soreness. In mid-March, he was diagnosed with a right shoulder impingement, but a month ago, with Thornburg making little progress, Dombrowski said the team was still trying to get a handle on what was wrong.
On Tuesday, Red Sox manager John Farrell said surgery "hasn't been recommended" for Thornburg. But that outlook changed this week when Thornburg traveled to St. Louis to be seen by Thompson, a specialist in thoracic outlet syndrome who has performed surgery on several pitchers, including New York Mets right-hander Matt Harvey.
"It's been a long exploration, basically, [to determine] what the problem has been," Dombrowski told reporters. "It's a situation where a lot of other avenues are exhausted before they get to this perspective."
Seeking an eighth-inning upgrade over 41-year-old setup reliever Koji Uehara, the Red Sox acquired Thornburg from Milwaukee for third baseman Travis Shaw, infield prospect Mauricio Dubon, Class A pitcher Josh Pennington and 18-year-old infielder Yeison Coca. That trade now appears lopsided, as Shaw enters play Thursday night with 11 home runs and an .887 OPS for the Brewers.
The Red Sox complained to Major League Baseball last year about the San Diego Padres concealing medical information before trading left-hander Drew Pomeranz to Boston in July. But Dombrowski said he believes the Brewers were "upfront" in sharing Thornburg's medical history before the trade.
"I don't believe in any way that Milwaukee knew this was taking place," Dombrowski told reporters. "They gave us all the information. There's no question that they were very upfront in that regard. When you make trades, at times, it's buyer beware. There's no way you would know this. You just hope you get a healthy player back for next year."
In February, Thornburg said he had "never had shoulder issues whatsoever" and traced the issue to a possible miscommunication over the requirements of the Red Sox's shoulder-strengthening program, specifically a significantly higher volume of exercises than he was used to with the Brewers.
"If anything, it might have fatigued my arm a little bit before the first outing [in spring training]," Thornburg said in March. "Or it possibly could've pointed out some weaknesses in my shoulder or something that wasn't working properly. People can say it was this, say it was that. I'd love to say exactly what it was because it would help me out a lot in the future. But I can't really say anything specifically, honestly."
Thoracic outlet syndrome typically occurs when nerves bridging the neck and shoulder become compressed or constricted, often causing weakness in the shoulder and numbness in the fingers and hands. The list of pitchers who have had surgery for thoracic outlet syndrome includes Josh Beckett, Chris Carpenter, Phil Hughes, Jaime Garcia, Matt Harrison, Tyson Ross and Matt Harvey.
In Thornburg's absence, the Red Sox have used several pitchers in the eighth inning of close games, with Matt Barnes handling most of those situations. Joe Kelly also has emerged as a late-inning reliever, and Carson Smith is expected to return from Tommy John elbow surgery after the All-Star break. Going into Thursday night's game, the Red Sox's bullpen has a 2.83 ERA, second best in the majors.
Also on Thursday, the Red Sox placed lefty Brian Johnson on the 10-day disabled list with a shoulder impingement after he left a start in the third inning Wednesday night.
Right-handed reliever Austin Maddox was called up from Triple-A Pawtucket. Maddox, 26, has a 1.33 ERA and three saves in 18 games between Double-A and Triple-A and has allowed one earned run in his past 13 innings.