Alvarez allowed four runs on seven hits in five innings against the Tampa Bay Rays on Sunday. He struck out three batters and walked one.
Marlins manager Mike Redmond said the team doesn’t have a timeline for his return.
"How long [will he be out]? I don’t know. That’s kind of the unknown right now. It’s really up to him and how quickly he feels better. We’re going to make sure that he feels good and confident before he goes out and pitches again.
"If he can’t pitch for a couple weeks but ends up finishing the season strong, that’s good not only for him but us."
Alvarez was an All-Star in 2014 and finished 12th in Cy Young voting. He had a 2.65 ERA and struck out 111 batters in 187 innings. He was tied for the major-league lead with three complete-game shutouts. He threw a no-hitter in September 2013.
Alvarez, 25, was the Marlins' Opening Day starter. Mat Latos, the No. 2 starter, allowed seven runs in two-thirds of an inning in his first start of the season.
Marlins ace Jose Fernandez began the season on the disabled list while he continues to recover from Tommy John surgery. He is expected back in May or June.
- Dan Gartland