The 26-year-old right-hander grew up in New Rochelle, N.Y., and attended Stony Brook University before being selected by the Marlins in the 18th round of the 2008 First-Year Player Draft. On Sunday, Koehler gets his first chance to start a Major League game in New York as he and the Marlins take on the Mets at Citi Field.
If all goes well, Koehler might be keeping the baseball: He's still searching for his first Major League win.
"I think it's going to be exciting for a lot of people," said Koehler, who has a 3.70 ERA in 41 1/3 innings this season. "A lot of people have helped me out along the way to get here. For them, I'm sure it will mean a lot.
"And I'm sure when I'm walking out there, when I'm warming up and stretching, I'm sure there will be a lot of faces that I haven't seen in a while. Some quick memories will flash back. But once the game starts, it's about the game."
Koehler has posted ERAs above four in each of his last two seasons with Triple-A New Orleans until this year, when he allowed just two earned runs over 17 innings before his promotion.
While he's struggled with his command at times, Koehler hasn't walked more than two batters in a game yet this season.
"I think it's exciting for him," manager Mike Redmond said. "I've really been impressed with his transition from being in the bullpen to starting, how easy that was for him.
"I think back to Spring Training when he struggled throwing strikes, and we had to send him down to the Minor Leagues. I know that was tough for him. But he went down there, and he got his work in, and he got the consistency that he needed. He came to the big leagues and got the opportunity to be a starter, and he's done a great job. It's really a testament to him."
On the mound for the Mets on Sunday will be left-hander Jon Niese, who had his last start skipped because of left shoulder tendinitis. The Mets could certainly use a boost from their Opening Day starter, who had a 5.93 ERA on May 11 but has allowed just three total earned runs over his last three starts.
Niese threw a bullpen session Wednesday and reported no soreness.
"I kept the arm angle up and made some pitches in the bullpen that had probably 85- or 90-percent intensity, and felt really good," he said. "I'm pretty confident that I feel good. How it felt before, in between each start, was night-and-day difference from how it felt [Wednesday]. It was good to get that rest."