Masahiro Tanaka called it a “deep hole” that he’s struggling to emerge from. But he insisted Monday that he isn’t hurt and said he is on his way to pinpointing the problem that has led to a slew of rough starts, from shaky to disastrous.

“Physically, there’s no problem at all. I feel fine,” he said through an interpreter, simultaneously agreeing that the beginning of this season has been “one of the worst slumps in my career.”

“I feel like I’m in a sort of deep hole, but again, I just can’t put my head down,” he added. “I have to lift my head up and work on the things that I need to work and try to fix what I need to fix and move forward. It’s a grind, definitely, it’s a grind and it’s frustrating, but I’m trying to get it right.”

In his last two starts, Tanaka has given up 14 runs, 16 hits (including seven home runs) and four walks in 4 2⁄3 innings. He has allowed 10 home runs in his last 13 2⁄3 innings and has a 1.60 WHIP. His ERA is 6.56, by far his highest this late in a season. It was never higher than 3.51 last year.

Injury becomes a particular concern with him, because he’s long pitched with a partial ulnar collateral ligament tear in his right elbow.

“I think as a coach, you look for signs that someone is hurt,” Joe Girardi said. “We haven’t seen a real drop in velocity, we haven’t seen him not being able to make a start. We haven’t seen him receiving extra treatment. He’s just in a little rut now that he needs to get out of. He feels fine.”

Tanaka said he’s been watching video of his previous starts and believes he has discovered a mechanical flaw. He’s been working with pitching coach Larry Rothschild on pitch sequence and command.

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“You can’t put your head down and ponder about it,” Tanaka said. “You just have to try to correct some of the things that you’re doing wrong, and that’s what I’m trying to do right now.”

Bird making progress

Greg Bird (ankle) is beginning his long journey back to the Yankees’ lineup. On Monday, he took 25 dry swings and 25 swings off a tee and ran the treadmill. “I felt great,” he said, “no problems.”