For now, the answer to that question remains quite murky. But Severino made a revealing comment Wednesday afternoon that will certainly raise eyebrows around Yankee Stadium.
Severino told reporters before Wednesday's game against the Boston Red Sox that he first felt the pain associated with his lat strain on the day he was scratched from what was to be his first spring training start.
"I think it was ... it happened that day," Severino said. "I don't know what happened there. I'm not really sure. But I think that was the day it happened."
Instead of being diagnosed with a lat strain that afternoon, March 5, Severino was officially sidelined with rotator cuff inflammation. The Yankees say that was all an MRI showed.
Because of that original diagnosis, the right-hander was required to be shut down for two weeks, before beginning a rehab program that general manager Brian Cashman once thought would get Severino back on a big league mound by May 1.
It was during Severino's rehab throwing program at the Yankees' complex in Tampa, Florida, that the team ordered a follow-up MRI. Three weeks into his throwing regimen, Severino hadn't quite advanced to the point at which he could throw off a mound. If he were simply dealing with inflammation, he should have been ready. So he and the team became alarmed.
"I was playing catch and I never [felt pain]," Severino said. "[But] it just wasn't progressing. It was really slow. I [knew] something was going on ... inflammation, that goes quickly. So I knew it was something else."
After undergoing the MRI last Tuesday in New York, Severino was told he had the lat strain, a more serious injury that occurs in the large lateral muscle that exists in a person's back. With the new diagnosis, Severino isn't allowed to throw until the second-to-last week in May. Since he'll be in need of a full "spring training" before pitching again, Severino likely won't be back until after the All-Star break.
Severino said he isn't sure why his original diagnosis was so different from what has come since.
"At that time [March 5], it was my back, and this time, they did the same thing. The same MRI in the shoulder," Severino said. "So I don't know what happened there."
Manager Aaron Boone said the Yankees are trying to figure out everything they can about Severino's injury and how it occurred. The pitcher still contends it was a slider he threw during his pregame warm-up 10 minutes before that scheduled spring training start that caused him the initial pain.
"We're just, as best we can as an organization, just trying to pinpoint [it]," Boone said. "You try and pinpoint injuries the best you can. From doctors to medical staff to the person to us, and try and get them back in the best treatment and the best answers.
"Sometimes there's injuries that happen and you know right away this is when it happened and this is exactly what it is. Some injuries are a little more gray and tougher to diagnose. The bottom line is, we feel like we know what he has and where it's at, and hopefully taking all the right steps to get him back as soon as possible and as healthy as possible."
Cashman told the New York Times that he is conducting a thorough investigation in order to unravel the mystery involving Severino's injury.
"I'm walking through the entire process. I'm not going to deliver a Mueller report whenever I conclude it," Cashman said. "But we're going through and I'm personally engaging every aspect."