KISSIMMEE, Fla. -- Starting pitcher Shaun Marcum joined the growing ranks of the Mets' injured players.
Marcum was diagnosed with an impingement in his right shoulder, the club announced Wednesday, one day after sending him to New York for a cortisone injection.
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"He said he gets it every spring pretty much, and so he just wanted to go get it cleaned up and get it done early," said manager Terry Collins, who believes Marcum may pitch on Monday or Tuesday.
General manager Sandy Alderson said he doesn't expect the veteran righty to land on the disabled list. But the Mets could have two-fifths of their starting rotation on the shelf to open the season, with Johan Santana.
The Mets signed Marcum this winter despite a long history of elbow and shoulder injuries. Marcum, who is 0-1 with a 4.66 ERA in three spring starts, was scheduled to start Thursday against the Cardinals. Instead, Jeremy Hefner will pitch.
Lefty Jonathon Niese will start Friday, which lines him up to start the April 1 season opener against the Padres.
Gee pleased with finish
Dillon Gee has allowed 11 runs in his last two starts, including five runs in four innings Wednesday night in a 7-5 win over the Astros. But he finished his outing by striking out the side.
"That was me," Gee said. "I was aggressive, the tempo way better, the ball was coming out great. Something clicked that last inning and I felt like my old self."
The Mets intend to carry two lefthanders in the bullpen. Josh Edgin appears to have the inside track for one job. Pedro Feliciano, Robert Carson and Scott Rice remain as the contenders for the other spot.
With two lefties on the team, the Mets have room for one more righthanded reliever, likely Jeurys Familia or converted submariner Greg Burke.
Outfielder Kirk Nieuwenhuis went 1-for-5 in minor-league action. It was his first game since suffering a bone bruise in his left knee on March 3.