Oakland is adding September call-ups on an as-needed basis, and the next two required will be Monday and Wednesday, when the team will bring up Raul Alcantara and Jharel Cotton to start against the Angels, sources told The Chronicle.

Alcantara, obtained in the same Andrew Bailey deal with Boston that brought Josh Reddick to Oakland before the 2012 season, has been sensational at Triple-A Nashville, where he is 4-0 with a 1.18 ERA. The 23-year-old has 32 strikeouts and has walked just three in 452/3 innings with the Sounds.

Cotton, 24, was acquired in the July trade that sent Reddick to the Dodgers, and he has done some eye-popping work with the Sounds, too, going 3-1 with a 2.82 ERA and coming within one out of a perfect game in his second start with Nashville. Opponents are batting .201 against him in his six starts with the Sounds.

Oakland needs starters with Sean Manaea and Andrew Triggs dealing with back issues. Triggs left Friday night’s start after one inning, and manager Bob Melvin said that Triggs was doing a little better Saturday but that the team won’t know when he can pitch again until he’s able to throw off a mound.

Phegley’s season over: Melvin said that catcher Josh Phegley is out of the hospital after a bout of strep throat plus inflammation in his surgically repaired right knee, “but we won’t see him play again this year, unfortunately.”

Phegley had arthroscopic knee surgery in July and initially had been expected back in a month to six weeks.

Briefly: Sonny Gray, who is on the disabled list with fluid in his elbow, is throwing at a distance of 105 feet. … Henderson Alvarez worked two innings in a rehab start at Class-A Stockton and allowed five hits and one run. ... Jose Canseco was on hand for his Bobblehead Night and declared it to be a “pre-steroid era” version of himself, “kind of skinny.” He said he knows the A’s are “not hitting at all. … People are making jokes, I should come back and be their DH.” ... Canseco said he believes former NFL quarterback Tim Tebow can make the big leagues, and he’d like to work with him.

Susan Slusser is a San Francisco Chronicle staff writer.

On deck

Sunday

vs. Red Sox

1:05 p.m. CSNCA

Rodriguez (2-6) vs. Graveman (10-9)

Monday

vs. Angels

1:05 p.m. CSNCA

TBD vs.

Alcantara (0-0)

Tuesday

vs. Angels

7:05 p.m. CSNCA

TBD vs.

Detwiler (1-3)

Leading off

Hot prospect: Nashville third baseman Matt Chapman, the recently promoted Texas League Player of the Year with Double-A Midland, hit three homers in the Sounds’ 6-5 loss at New Orleans on Saturday. He also had a single.

— Susan Slusser