New York Mets ace Jacob deGrom is dealing with right forearm tightness and will miss his scheduled start Monday against the Cincinnati Reds, manager Luis Rojas said Saturday.

An MRI on deGrom's forearm revealed no structural damage, according to Rojas, and he is considered day-to-day.

Rojas said deGrom felt the tightness while throwing a side session Friday and did not finish the session. He is currently receiving treatment and will not resume throwing until the tightness subsides.

Rojas added that deGrom said Saturday that he felt similar tightness during a bullpen session right before the All-Star break as well. DeGrom did not attend Tuesday night's All-Star Game at Coors Field, electing instead to spend time with his family and rest for the second half.

The two-time NL Cy Young Award skipped an outing between April 28 and May 9 due to discomfort in his right lat muscle, then did not pitch again until May 25 while spending time on the injured list with what the Mets said was tightness in his right side. DeGrom left his June 11 outing against San Diego after six innings because of flexor tendinitis in his right arm.

Rojas said Saturday that those ailments, including the right forearm tightness, are all unrelated.

DeGrom is 7-2 with a majors-best 1.08 ERA and 146 strikeouts for the NL East-leading Mets.

The Associated Press contributed to this report.