When Smith had an MRI exam at that point, there was no structural damage found in the ulnar collateral ligament. But the MRI the club conducted at the end of last week showed a significant difference.
"I admit that even in that MRI I could see the difference between the one taken in March and the one taken on Friday," said Red Sox president of baseball operations Dave Dombrowski. "I couldn't tell you what it meant, but I could tell you that there was a significant difference, so it's unfortunate. Our doctors felt there was a tear at that point."
The Red Sox sent the images to Dr. David Altchek in New York, and he confirmed the tear and performed the surgery.
When the Red Sox traded lefty starter Wade Miley to Seattle for Smith back in December, they envisioned the side-winder being a key part of the bullpen. But that is now tabled for roughly one year.
"We're going to miss him," said Red Sox manager John Farrell. "He was an acquisition this winter that, as we know, was likely to play a pivotal role, particularly against tough right-handed hitters in our division. In light of his absence, I really like our bullpen."
The beauty of Smith's arrival was that it would lessen the workload for Farrell's top three relievers -- Craig Kimbrel, Koji Uehara and Junichi Tazawa. Farrell feels he still has enough depth to avoid overextending anyone.
Matt Barnes, Heath Hembree and Robbie Ross Jr. will need to continue to get big outs when called upon.
Dombrowski will also keep an eye on the trade market, but things likely won't heat up on that front until July.
"There's still quite a bit of time between now and the Trade Deadline," Dombrowski said. "So you continue to watch that. I feel comfortable the way it is now, but we'll continue to wait and see. I did not anticipate this, and that's really why we got Carson -- to give us more depth in case something did happen at one point. But we'll continue to watch it and see what takes place."
Though some will theorize that Smith's motion takes a toll on his arm, Dombrowski thinks it would be counterproductive to have the pitcher change to a more over-the-top style when he returns.
"Usually they have that delivery just because they feel more comfortable," said Dombrowski. "A lot of times if you ask them to change their delivery, that's when they hurt their arm."
A former Major League pitcher himself, Farrell underwent Tommy John surgery during his career and feels for Smith.
"Tommy John, that bell rings loud when a pitcher is faced with that and when it's recommended that they go through it," said Farrell. "Certainly, the advances in the procedures are there, but sure, he's got a lengthy road ahead of him now. But it's one that's a clear-cut path."