PORT ST. LUCIE — David Peterson had a solid camp and Tylor Megill struggled late, leading to the expected announcement Monday regarding the Mets’ rotation vacancy.

The left-hander Peterson will receive the start Friday in Miami and Megill is headed north to pitch the opener for Triple-A Syracuse at Worcester. Peterson will follow Opening Day starter Max Scherzer in the Mets rotation.

Peterson last season appeared in 28 games for the Mets — 19 of which were starts — and pitched to a 3.83 ERA. He and Megill began the spring as rotation depth, but Jose Quintana’s rib surgery that will keep him sidelined at least into July created a need for the Mets.

“I think a lot of it came down to just feeling I was in a good spot with all the pitches, mechanics, feeling by the end of spring training I was in a really good spot, built up to start the season,” Peterson said.

In his four appearances this spring, Peterson didn’t allow an earned run, striking out 13 with eight walks in 12 innings. The Mets weren’t committed to keeping Peterson in the rotation just for the sake of having a left-hander, and Megill at one point appeared as maybe the favorite for the job, but struggled over his final two appearances in the Grapefruit League with 10 walks over 8 ²/₃ innings. He finished the spring with a 3.71 ERA.

“It sucks,” Megill said. “I want to be up playing with [the Mets]. All I can do is just work and be ready when my name is called.”

That opportunity could occur as soon as mid-April, when the Mets begin a 10-game West Coast trip without a day off that could include an added arm in the rotation. Buck Showalter indicated a sixth starter on that trip is one possibility the Mets are considering.

Megill last season was the Mets’ Opening Day starter and pitched to a 1.93 ERA over his first five starts before going on the injured list. Megill had a second IL stint (with a shoulder impingement) that lasted half the season and he was moved to the bullpen upon his return and struggled.

“I think he’s a guy that understands he’s going to pitch for us and be a big need for us,” Showalter said. “He’s very mature about understanding where this thing is. He’s still young and he’s healthy. I know he’s frustrated with his command, but a lot of these guys when they take a deep breath and get away from it they kind of settle into who they are.”