Canning is expected to throw again after receiving treatment to see how his elbow responds, at which point the next step will be determined, the source said.
Canning pitched two scoreless innings against the Los Angeles Dodgers on Wednesday and had discomfort after coming out of the game, manager Joe Maddon said.
Maddon acknowledged his worry, saying, “He’s had a history, so of course you’re concerned.”
The 23-year-old right-hander went 5-6 with a 4.58 ERA last season before being shut down in August with elbow inflammation.
The Angels had expected that Canning, a second-round pick out of UCLA in 2017, would take a spot in the rotation this season.
“He’s got a fabulous arm,” Maddon said. “He’s got a great future. We want him well.”