ST. PETERSBURG, Fla. — Masahiro Tanaka will not take his next scheduled start on Monday in Toronto after an MRI taken Thursday morning showed a “slight, slight, slight strain” in his lower right forearm area, according to Yankees manager Joe Girardi.

Girardi stressed the injury is not near the ulnar collateral ligament that Tanaka sustained a small tear in during the 2014 season and has been pitching with since.

“It’s not by the ligament, it’s way down low,” Girardi said. “He’s not going to pick up a ball for five days and hopefully he’ll be ready to go soon after that.”

Tanaka allowed four runs, all on four solo home runs in the third inning, over six innings of his start against the Rays Wednesday night. He complained of soreness in the arm after the start and was sent for an MRI Thursday.

“From what we’ve been told, it’s not the UCL, which is good news,” pitching coach Larry Rothschild said. “He had trouble with his slider [Wednesday night]. I don’t think it was bothering him but it just wasn’t right.”

Through his translator Thursday, Tanaka described the sensation he felt in his lower arm as “tightness.”

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“No pain at all,” he added.

Tanaka, who is 14-4 with a 3.07 ERA, said he is not concerned.

“I’m not worried,” Tanaka said. “The team is being cautious. I’m confident I’ll be able to come back soon.”

But Rothschild, a former big-league pitcher and coaching lifer, knows nothing’s guaranteed with pitchers and their arms.

“I can’t answer that question,” he said, asked if Tanaka will pitch again this season. “I’ll know in five days. I can’t sit here and take out a crystal ball and tell you what he’s going to do. Hopefully in five days it’s cleared out.”

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The timing, needless to say, is not ideal with the Yankees hoping for a miracle down the stretch to get into the postseason.

“It’s very disappointing,” Tanaka said. “We’re making a push, it’s a very important time for us. This is not the time you want to skip anything.”