That is what the Mets are trying to determine. Mejia was available to pitch the ninth inning Sunday if needed, a day after earning his first career save. He entered this weekend not having pitched back-to-back days as a reliever since 2012.
"And that's what we've got to get over," Collins said. "That's the thing we've got to find out: can he handle it physically? And if he can, he'll be as good as there is in this game, because he's got that kind of stuff."
The issue, Collins intimated, is at least partly in Mejia's head. Since enduring a litany of arm injuries from 2010-13, Mejia has grown fearful that any variance from a strict routine will put him at risk of further arm trouble. That is a significant reason why Mejia was hesitant to convert back to relief work in the first place.
When asked Saturday if he might be available to pitch again Sunday, Mejia -- unprompted -- began discussing his own injury history. He lauded the Mets' coaching staff for giving him plenty of notice before Saturday's outing, saying: "I feel comfortable when I know I'm going to pitch."
"There is an issue because his past has been arm issues," Collins said. "That's why we're trying to be careful with him until he overcomes the fact that he's going to be OK. It's going to take a little while for him to pitch and him to pitch back-to-back days to where, 'Hey look, I'm going to be OK.' That's the No. 1 issue is health. He's as worried as anybody that something's going to happen."
Once ranking among the Mets' most promising pitching prospects, Mejia injured his rotator cuff while pitching out of the bullpen in 2010 and, essentially, took more than three years to recover. The following season, Mejia tore an elbow ligament and had Tommy John surgery, before undergoing yet another surgery to clear out bone chips in his elbow last September.
He reported to Spring Training healthy, but wary.
All the other tools, Collins knows, are there, which is why the manager wants Mejia -- not Jose Valverde, Daisuke Matsuzaka or any of his other closer candidates -- to settle into the ninth inning for good. Since converting to relief work early last week, Mejia has contributed three scoreless outings with five strikeouts and no walks. His velocity, which averaged around 93 mph as a starter, has climbed to nearly 95 as a reliever.
Mejia also enjoys the work, even if he did prefer starting.
"The only thing that I say is it's just one inning, one spot," Mejia said. "The seventh, eighth, ninth all feel the same."