Where this leaves Parnell remains to be seen. If Mejia takes the closer's job and runs with it, there will be no ninth-inning duties waiting for Parnell when he returns next spring.
"That's how I got in there," Parnell said, referencing how he assumed the job from Frank Francisco when Francisco was injured in the spring of 2013. "Injuries happen, and opportunities arise. As a baseball player, you've got to jump at those opportunities. If Mejia does that, then that's what he was born to do, and that's great.
"I love closing. I want to do it, and I know I can do it, but whatever happens, happens."
Parnell excelled in his first full-time taste of the role last summer, saving 22 games in 26 chances with a 2.16 ERA. But he underwent surgery to replace a herniated disc in his neck in August, lost significant weight and struggled to regain his velocity this spring. After blowing a save on Opening Day, he underwent an MRI that revealed a partially torn MCL in his pitching elbow.
The Mets initially replaced Parnell with Jose Valverde and then Kyle Farnsworth before turning to Mejia last week. Still just 24 years old, Mejia pitched on back-to-back nights on Wednesday and Thursday for the first time in two years, saying on Friday afternoon that he feels "normal."
"I think [Mejia] is relieved," Collins said. "I think he's happy that he feels the way he does. His biggest concern was, 'I've done this and I got hurt, and I don't want to try it again.' I don't think it will be very long before three nights in a row is within reach."
But with every step forward that Mejia takes, it becomes less and less likely that Parnell will ever reclaim his old duties. For now he will simply work on rehabbing his arm back into shape, with plans to fly to Florida next week. He will stay there for the rest of the summer, throwing alongside fellow Tommy John patients Matt Harvey and Jeremy Hefner in an effort to be ready for Opening Day 2015.
What happens after that will unfold in time.
"I know I can do that job," Parnell said. "I know several other people can do that job also. Whatever happens, happens. I'm just focused on getting healthy right now."