PITTSBURGH -- The timetable for Sean Manaea’s return from left shoulder surgery continues to look up, as he’s scheduled to throw his first bullpen session on Tuesday.

Manaea underwent season-ending arthroscopic surgery on his left shoulder, performed by Dr. Neal ElAttrache, on Sept. 19, 2018. The procedure helped create more space in the left-hander’s joint capsule and also repaired his labrum.

According to head trainer Nick Paparesta after the surgery, Manaea had dealt with chronic shoulder impingement throughout the prior two seasons, and it finally got to a point where the 27-year-old was unable to pitch without pain. He’d been placed on the 10-day IL with left shoulder issues twice, in April 2017 and August 2018, before opting for surgery.

The progress Manaea has made has raised the possibility of a return to the rotation by the end of the season. At the outset of April, when Manaea was throwing at 90 feet, A’s manager Bob Melvin said he felt like “the potential is there” for his ace to impact the rotation late this season.

That would be good news for the A's, especially if they can orchestrate another run at the postseason; Oakland is currently last in the AL West at 15-20 after the 6-4 loss to the Pirates on Saturday night, but the club made its charge last season primarily in the later part of the year.

Across 27 starts last season, Manaea went 12-9 with a 3.59 ERA, striking out a team-high 108 batters. He threw the seventh no-hitter in A’s history on April 21, 2018, against the Red Sox.

Laureano out with foot pain

Ramon Laureano was scratched from Saturday’s starting lineup after fouling a ball off his foot on Friday night. He stayed in the game initially despite the pain, but he exited in the seventh.

“It’s one of the reasons I got him out of the game last night. Get him out, get him some treatment,” Melvin said. “There are certain ones you foul off and you play through. And there are other ones that set you back a little bit.”

Robbie Grossman started in center field Saturday for the first time since 2016, batting second. Laureano entered in the ninth as a pinch-hitter, replacing Skye Bolt in the No. 9 spot, and grounded out to short.

Injury notes

• Matt Olson (right hamate bone) homered in a rehab start with Triple-A Las Vegas on Friday night, finishing 1-for-5. Melvin said Olson will continue his stint with the Aviators Saturday at first base, then will likely be the designated hitter on Sunday. Olson is a possibility to return within the coming week, Melvin said.

• Nick Martini (right knee sprain; hyperextended back) will run the bases on Tuesday, according to Melvin. He will likely begin his rehab assignment if all goes well.

• Jharel Cotton (Tommy John surgery) has been throwing in extended spring training, and Melvin said he believes Cotton will be up to three innings his next time out.