KANSAS CITY, Mo. — Aroldis Chapman told reporters Sunday he had been feeling discomfort in his left shoulder for a period of “weeks.”

That news that came as, well, news to Brian Cashman.

“I’ve been doing this 20 years and it’s a great mystery,” Cashman, the GM since 1998 and a part of the franchise since 1986, said Monday of players not always being straightforward with how they feel physically. “It’s like if you see something, say something. We preach to our players, if you feel something, say something. He didn’t say anything.”

Not until Friday night when the 29-year-old closer mentioned to trainer Steve Donohue that his shoulder didn’t feel quite right. Chapman underwent an MRI Saturday, which revealed no structural damage but showed right rotator cuff inflammation, landing the lefthander on the 10-day DL Sunday afternoon.

Chapman is expected to be out for a minimum of a month, which thrusts Dellin Betances into the closer job and Tyler Clippard into the primary setup role.

“I don’t have an answer other than to tell you every box was checked by the staff, there was no deviation [from his routine],” Cashman said of Chapman. “It is what it is. You respond to the input you’re given.”

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Chapman, given the biggest contract ever to a reliever in the offseason (five years for $86 million), had seven saves with a 3.55 ERA in 14 games. But he was unable to make it through his last two outings, May 7 at the Cubs when he blew his first save of the season, and Friday against the Astros, removed from both appearances after two-thirds of an inning.

The radar gun certainly didn’t indicate something was amiss; Friday Chapman threw 24 pitches, six of which reached 100 mph.

There had been some early signs of trouble in late April when Chapman, after an erratic save (his fifth) April 26 in Boston, briefly grabbed at his left arm after recording the final out. Afterward he said he was Ok.

Cashman said Monday his desire is for players not to “turn our staff into veterinarians.”

And, no, he did not mean it in the coarse way it might have sounded.

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“I mean that in the way that you’re not able to convey what hurts if you’re an animal,” Cashman said. “If the patient can’t tell you there’s a problem, it’s guesswork . . . all I can tell you is in real time the questions were asked and the answers were given, that’s all I can control. If you’re denied a piece of the puzzle, you can’t complete the puzzle.”