Johan Santana will have an MRI on his back Tuesday that will determine his status for the remainder of the season.

Santana had already been dealing with lower back pain, but had declared it as nothing more than minor.

"He came in stiffer today than he had been," Mets manager Terry Collins said. "They got him loosened up, he threw his pen, felt fine when he was done, got a little tight, had the doctor look at it and the doctors thought they should take a look at it [today]."