Jeff Karstens came into camp determined to grow into a more reliable pitcher by “listening to my body.”

Tuesday morning, that body told him to take a step back.

The right-hander was scratched from his scheduled turn to throw batting practice after he complained of “a little soreness” in front of his upper shoulder, in “the biceps area.”

Anybody else, the development could’ve been easily shaken off. It is early. The past couple of mornings have been unseasonably chilly, not ideal throwing weather.

But this, after all, is Karstens. He could extract only 90 2/3 innings out of his body last season. That fragility, in fact, is the very reason the Pirates at first non-tendered him, then delayed bringing him back on a new contract until Jan. 17.

“I just want to play it smart. It doesn’t make any sense to push it,” he said. “I’ll still play catch (on flat ground). We just want to be smart about this, wait a couple days,” he said. “It’s not September. I don’t want another Arizona.”

Karstens referred to his start last April 17 against the Diamondbacks, which he had to leave after one inning with tightness in the shoulder. Including a strained-groin glitch in his rehab program, he didn’t resurface until late June.

Karstens’ timeout, even briefly, dials up the already-intense competition for spots in the starting rotation.