Shaun Marcum’s next scheduled start is in jeopardy after the Mets pitcher yesterday underwent an MRI exam on his upper back, according to a club source.

The veteran right-hander wouldn’t discuss the issue when approached after the Mets’ 9-1 victory over the Diamondbacks last night.

“That’s for me and the club, so I’m not going to talk about it,” Marcum said.

A source said the Mets considered placing Marcum on the disabled list yesterday, but decided to wait. If Marcum can’t pitch on Saturday in Milwaukee the most likely candidate to start would be right-hander Carlos Torres.

Marcum, 1-9 with a 5.03 ERA, began the season on the disabled list with neck stiffness. He was in visible discomfort on Monday, when he allowed three earned runs over six innings and received a no-decision in the Mets’ 4-3 victory over the Diamondbacks in 13 innings.

Manager Terry Collins has said Anthony Recker might get more playing time behind the plate with John Buck struggling badly. Recker came into last night batting just .157, but with two out in the fifth crushed Patrick Corbin’s 2-1 changeup to left for a solo shot, then added a clutch RBI single when play resumed in the seventh.

Corbin came in 9-0 with a 2.22 ERA, trying to become the first lefty starter to begin a season 10-0 since the Yankees’ Ron Guidry in 1978. But the Mets, who had the worst team batting average in the majors, roughed him up.