The New York Mets have designated left-hander Aaron Laffey for assignment, and called up reliever Robert Carson from Triple-A.

"Robert's been throwing the ball very well down there," said Mets manager Terry Collins. "So we're gonna give him a shot."

Laffey had been serving as the Mets' fifth starter, due to injuries to Johan Santana and Shaun Marcum. Santana is out for the season, but Marcum could rejoin the Mets later this week.

Marcum, who's on the DL with nerve inflammation in his neck and shoulder, will throw 70-75 pitches in a rehab outing on Monday. If that goes well, he will likely start for the Mets on Saturday against the Philadelphia Phillies.

"Shaun's getting ready," Collins said. "When he gets here, probably 90, 95 pitches would be max for him, his first start. But the kind of pitcher he is, you look up and 90 pitches and he's in the seventh inning, because he's a guy who pitches to contact. He's not a strikeout guy, he's a ground-ball guy. But again, we'll wait to see how he comes out of tomorrow."

Carson was 1-0 with a 1.17 ERA in eight appearances this year with the Las Vegas 51s. The left-hander appeared in 17 games for the Mets last season, giving up seven runs in 13 1/3 innings, for an ERA of 4.73.