"It's tough to say," said Marcum. "The main thing for me is I have to keep the ball down and locate my pitches. If I don't do that, whether I'm at 100 percent or 50 percent, it doesn't really matter. I just have to go out there and locate, try to get ahead of hitters and have them put the ball in play early."
Marcum may not have pitched for the Mets before, but he will have a built-in security blanket in catcher John Buck. Buck, who entered Friday the National League leader in RBIs (22), caught Marcum with the Blue Jays during the 2010 campaign, so they'll both know what to expect from each other.
"I've played with John before. Many times. And I've faced the Phillies many times, too," said Marcum of his first assignment. "We played them in 2010 when John and I were with Toronto in Interleague. Having him back there -- and that comfort level -- will be a nice advantage for me."
Marcum, 31, has a 57-36 record with a 3.76 career ERA, and he's been even better in his brief exposure to the National League. Marcum went 20-11 with a 3.60 ERA in 54 starts for the Brewers, and manager Terry Collins liked what he saw in Spring Training.
"We know what kind of pitcher he is," Collins said. "Obviously, it's all about the health issues. He says he's feeling great. We know he's going to sink it, he's going to change up, he's going to work the corners. He's going to work fast. He's one of those guys -- even though we're going to watch him pretty close pitch-count wise -- he's going to get us to the fifth or sixth inning easy."
The Mets will likely demote a reliever to make room for Marcum, but Collins wasn't ready to make that announcement before Friday's game. Marcum, who has never logged more than eight losses in a season, said that he missed competing with his teammates over the last few weeks.
"I'm sure I'll have a little bit of adrenaline. A lot more than I had in extended spring games," he said. "At the same time, you've got to know how to control it and use it to your advantage. Know when to back off, know when to add on a little bit. ... I'm definitely excited to get out there."