"I'm concerned -- I don't know what's going to happen," Escobar told reporters. "I don't even know if I'll be able to pitch again."
Escobar, who won 18 games in 2007 and was in Cy Young Award conversations before shoulder inflammation surfaced in September, had been throwing soft-toss for a week when he felt pain return to the shoulder on Saturday. He'd been shut down this spring, after aggravating the shoulder in a workout in December.
"I'm still young," he said. "I'll be 32 in two weeks, but retirement is getting into my head, because it's hard to rehab. I want to be out there playing, and I've done everything I can do to be healthy."
Asked about Escobar, who expressed fear for his career earlier in the day with ongoing shoulder issues, manager Mike Scioscia said: "There's no certainty where Kelvim is going to be a month from now. We're still optimistic we're going to see him on the mound at some point."
Escobar will continue to try to strengthen the shoulder with workouts, but he admitted that surgery could be a possibility.
"They would look at it and fix whatever I have," he said. "But that would take 10 months to recover from. They're not sure I'd be able to come back after surgery. This could be the end of my career."
Escobar is in the second year of a three-year, $28.5 million contract.
Lyle Spencer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.