The move, which was announced by Baltimore president of baseball operations Andy MacPhail following the O's 4-1 Opening Day win over the Rays, will sideline Matusz anywhere from "3-5, 4-6 weeks" and is a significant blow to a team without a lot of starting pitching depth.
With Justin Duchscherer on the DL (left hip soreness) and now Matusz, Baltimore's rotation candidates have been whittled down to five, forcing the team to recall top pitching prospect Zach Britton who will take Sunday's start in place of Chris Tillman.
Tillman, who was named the team's fourth and final starter out of camp -- given some early off-days -- was pushed up to Saturday. Brad Bergesen was another option, but he's still building up arm strength after suffering a right forearm contusion and at this point, the team was concerned with the length he would be able to give them as a starter.
"With the duration that we think it is likely Brian will be out, we are going to need the fifth starter," MacPhail said of the decision to start Britton's service clock. "So we might as well just plug Zach in now as opposed to waiting until the 9th or 10th [of April]."
While Friday's news was surprising, Matusz admitted he had been feeling some moderate soreness and discomfort for the last four or five days. It wasn't until Thursday that it turned into something more serious.
"It went from being sore to absolutely hurting," said Matusz, who received a cortisone injection to help speed his recovery. "It was painful. I went to the trainers and tried to get treatment [Thursday]. I got treatment [Friday] and went out to throw and I just couldn't do it, it hurt so bad. I couldn't throw the ball 10 feet."
He was immediately scratched from Saturday's start and the ensuing MRI showed the strain, the latest -- and most serious -- injury in a frustrating spring for Matusz. The 24-year-old was hit with a line drive in his left biceps Monday and had a wart removed on the middle finger of his pitching hand earlier in camp. In five games (four starts), Matusz went 0-2 with a 5.93 ERA.
"It's not fun, especially this time of the season, all the excitement, [and] how well we played [on Friday]," Matusz said of his injury. "It's really unfortunate. I'm just going to do whatever I can and work as hard as I can to get back out there. That's pretty much all I can do. Put it behind me and work hard to get back to where I want to be, and that's up here competing."
"It's tough," said starter Jeremy Guthrie, whose eight scoreless innings Friday night lost some of their luster given Matusz's injury. "I know how much it means to him. I told him, out of all the 25 guys here, you take somebody out of the lineup for the first game and I think it would hurt him the most.
"I feel really bad for him and I know he feels terrible that he's going through something that he's never gone through. That's bad news for the team, but we're going to try and pick him up the best we can without him, knowing when he comes back, he'll only make us that much better."
Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Twitter @britt_ghiroli. This story was not subject to the approval of Major League Baseball or its clubs.