NEW YORK -- Unhappy with their current bullpen mix, the Mets made a move Sunday morning to bring in a fresh arm, recalling left-hander Robert Carson from Triple-A Las Vegas. Once considered a favorite to make the Opening Day roster, Carson posted a 1.17 ERA over 7 2/3 innings with Las Vegas, striking out seven against two walks.
"He's been throwing very well," manager Terry Collins said. "Rob gives us another option, especially against a team like the Nationals that have so many left-handers in the middle of their lineup. They're all good hitters. But we need to just have a left-hander available that if you're going to get beat, you want them to get beat by somebody who doesn't hit them very good."
To make room for Carson, the Mets designated struggling lefty Aaron Laffey for assignment -- the strongest indication yet that Shaun Marcum will be ready the next time the Mets need a fifth starter on Saturday. Laffey had been Marcum's replacement in the rotation, posting a 7.20 ERA in two starts and two relief appearances.
"It's been tough for him," Collins said. "But we just thought it was important to bring up a relief pitcher, so we did."
That reliever is Carson, who seemed on track to make the team before the Mets broke camp with Scott Rice instead. Carson and Rice give Collins multiple left-handed options outside of Josh Edgin, who has given up seven runs over his last three appearances.
Should that trend continue, Edgin may rapidly lose work to Carson.
"I was disappointed in myself when I got the news, but I knew I had to keep working," Carson said of not making the club initially. "So I went down and went back to the drawing board and kept working, and got all my stuff consistent down there and tried to command the strike zone. And that's what I did."
Anthony DiComo is a reporter for MLB.com. Follow him on Twitter @AnthonyDicomo. This story was not subject to the approval of Major League Baseball or its clubs.