What a pain in the neck.

Shaun Marcum will be examined by Mets doctors in New York today for what manager Terry Collins described as “discomfort” running from the right-hander’s shoulder to neck. Marcum was scratched from his simulated game appearance on Tuesday in Port St. Lucie, Fla., because of the discomfort.

With Marcum, who hasn’t pitched in more than two weeks, no longer a possibility to pitch Sunday against the Marlins, the manager said he expects lefty Aaron Laffey to take that turn in the rotation.

The Mets began stretching out Laffey for starting duty toward the end of spring training, after it became evident the team was thin on rotation depth. Collins said rookie Collin McHugh and journeyman Chris Schwinden are also on the radar, but Laffey is the most likely candidate for Sunday.

“Hopefully [Laffey] comes in Sunday and pitches very well,” Collins said before the Mets faced the Padres last night at Citi Field. “And if he does, he most likely will get another start. We’ll just take it one start at a time right now.”