(Julio Cortez/AP)

“I’m not worried,” Morse said. “And I get worried. It’s early. There’s plenty of time to get going.”

Morse first felt tightening in the side of his back, just below his arm pit, two or three days ago. “It just feels like a little knot,” Morse said. It affected him only when he threw, not when he ran or swung the bat. Morse played as the designated hitter in Sunday’s game, and Monday he did not play at all.

Morse was scheduled to play today in left field today, his first action in the field.

“Today just warming up, it feels kind of tight,” Morse said. “There’s no reason to push it this early. It’s something that, you need a little break, a little rest. You’re probably a little overworked or something.”

Morse said he will still take batting practice over the next few days, and likely return to throwing and game action by the end of the week.

“It’s a tweak,” Nationals General Manager Mike Rizzo said. “Just a day. He’s too big to get hurt.”