"I saw him moving his wrist and elbow," manager Alex Cora said. "I didn't like that. We've got to be smart about this."
Whitlock missed 27 games earlier this season because of right elbow ulnar neuritis.
"It doesn't really feel very nervy, so it's not really like that," said Whitlock, who is expected to undergo an MRI on Monday.
Whitlock also missed 10 games at the start of the season while recovering from right hip surgery. He's 4-3 with a 5.23 ERA in 10 starts.
Left-hander Brennan Bernardino took over in the second and pitched 1⅓ innings.
The Associated Press contributed to this report.