Hyun Jin Ryu left his start Wednesday night against the Chicago White Sox after four innings because of tightness in his pitching forearm.

Ryu is 2-0 with a 5.33 ERA in six starts for the Toronto Blue Jays this season. He missed time in April and May because of soreness in his forearm, but he had gone 2-0 with a 1.72 ERA in his past three starts since returning May 14.

He'll undergo an MRI to determine the extent of the latest issue.

"I don't think it's similar from my last start," Ryu said through an interpreter. "It felt more similar to earlier in the season when I was hurt."