MIAMI -- Right-hander Rafael Montero's return to Las Vegas will take a detour. After making a spot start for the New York Mets on Tuesday in Miami and getting demoted following the game, Montero complained of tightness in the back of his throwing shoulder.

Montero will be sent to New York, where he will undergo an MRI and be examined by team doctors at the Hospital for Special Surgery on Thursday, assistant general manager John Ricco said.

For now, Montero's demotion remains in effect. If there is any gravity to Montero's issue, the demotion may be rescinded and Montero could be placed on the major-league disabled list.

Montero, 24, took a scoreless effort into the sixth inning Tuesday against the Miami Marlins but ultimately was charged with three runs in 5 2/3 innings.

"Hopefully it's nothing serious, but just to take a look at it, he'll meet with the doctors tomorrow morning," Ricco said.

Ricco said he is unaware of any previous shoulder issues involving Montero before the prospect mentioned it to trainer Ray Ramirez late Tuesday evening.