Jack Flaherty left Sunday's start against the Chicago Cubs because of stiffness in his right shoulder.
Flaherty threw 49 pitches, allowing one hit, walking two and striking out two.
He was not available after game. Oliver Marmol said Flaherty had a "dead arm sensation."
Flaherty, 26, didn't make his debut this season until June 15 because of an ailment in his right shoulder. He had a platelet-rich-plasma injection in his shoulder in early March to treat inflammation.