OAKLAND — It's looking less and less likely that A's ace Sean Manaea will return this season.

“It is a long shot,” A's manager Bob Melvin said Friday. “Every day that we go along, it's more of a long shot.”

Manaea went on the disabled list August 26 with what was later found to be left shoulder tendinitis, and the lefty still has not resumed any baseball activity.

“He has not progressed enough to where he can throw yet,” Melvin said. “He's going to have a tough time coming back. The longer we go without him throwing, the more difficult it will be for him to come back, unfortunately.”

Manaea couldn't provide any further update, saying simply, “Right now we're just taking it day by day.”

The A's also received bad news on right-handed pitcher Andrew Triggs, who has been out since May with nerve irritation in his right forearm. The A's had been hoping Triggs could join the bullpen for the stretch run, but he suffered a setback after striking out two in 1 2/3 innings with Single-A Stockton on Wednesday.

“He started to get some symptoms like he did before, so we'll have to shut him down and figure out where we go from there,” Melvin said.