"Robert's been throwing the ball very well down there," said Mets manager Terry Collins. "So we're gonna give him a shot."
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.
The 24-year-old said he was disappointed he didn't make the big-league club out of spring training, but worked on his fastball command at Triple-A, plus his breaking ball, changeup and cutter.
"I went back to work," Carson said. "Now I'm back here, and I'm happy to be here."
The Mets could use some help in the bullpen. On the season, their relievers have an ERA of 5.47 -- the worst mark in the major leagues.
Laffey, 28, signed a minor league contract with the Mets in December. He didn't make it out of the fifth inning in either of his starts this year. In four overall appearances and 10 innings of work, he allowed eight runs on 16 hits, for an ERA of 7.20.