PORT ST. LUCIE, Fla. -- Jacob deGrom underwent an MRI on Friday morning, a day after the Mets right-hander said he felt tightness in the back of his right shoulder while playing catch. The team scratched deGrom from his originally scheduled Grapefruit League start against the Cardinals, replacing him with right-hander Félix Peña.

According to manager Buck Showalter, deGrom felt fine during his routine game of catch on Thursday until his last couple of throws. He looked strong over his first two Grapefruit League starts, allowing one run in five innings with 10 strikeouts. deGrom had also made some concessions in the name of staying healthy, lifting slightly heavier weights this winter and dialing back his velocity a few ticks in spring.

Only time -- plus deGrom’s test results -- will tell if this is just a minor blip or something that could force him again to miss significant time. Injuries are nothing new to deGrom, who missed the entire second half of last season due to inflammation in his right elbow and forearm, and who has endured back, elbow and shoulder scares throughout the past two seasons. When healthy, deGrom has remained an elite pitcher, posting a 1.08 ERA with 146 strikeouts in 92 innings last season. But deGrom has made only 27 starts the past two years.

If deGrom is not healthy enough to take the ball on Opening Day, the Mets could rather easily slide No. 2 starter Max Scherzer into that slot on regular rest. Tylor Megill or David Peterson would then enter the back of the rotation in his place.

As of Friday morning, however, the Mets were not thinking that far into the future. They were awaiting deGrom’s MRI results before determining next steps.