MESA, Ariz. -- With 2022 All-Star right-hander Paul Blackburn set to open the season on the injured list, there is suddenly an opening at the top of Oakland’s starting rotation, at least for now.

Which means James Kaprielian’s efficient performance in a 7-2 Spring Training victory over San Francisco at Hohokam Stadium on Friday could not have been more welcome.

Kaprielian gave up one run and five hits while striking out four in four innings, his longest outing of the spring and the most encouraging sign yet that the offseason surgery to repair the AC joint in his right shoulder is behind him.

“He threw strikes, pounded the zone,” manager Mark Kotsay said. “All good signs. Today was a little more stress to the shoulder. We’ll see how he recovers. At this point, if we can keep pushing, keep getting him built up, he should have the opportunity to open with us.”

Kaprielian took the mound about four hours after Kotsay said that Blackburn will open the season on the IL because of a fingernail avulsion to his right middle finger that makes it impossible for him to grasp the ball properly and will cost him at least two starts. Backup catcher Manny Piña also will open the season on the injured list with left wrist inflammation.

While nothing had been announced, it had been believed that Blackburn would start Oakland’s regular-season opener March 30 against the Los Angeles Angels at RingCentral Coliseum. There is no timetable for Blackburn’s return.

“It’s pretty unfortunate,” Kaprielian said. “He’s going to be fine. The rest of us just have to stay ready. We are going to take pride in being a family as a staff and be comfortable passing the ball to the next guy."

Kaprielian threw 59 pitches (43 strikes), and was particularly effective with his off-speed pitches, although he said he felt his stuff was not his best. He gave up four singles (one a bunt) and a double, and retired the last six batters he faced after giving up two singles and a run to the first two Giants’ batters in the third.

He struck out three of the last six batters he faced on off-speed pitches, and he registered his top velocity in the fourth, a 95 mph fastball to Roberto Pérez, the last better he faced.

JP Sears originally was scheduled to start in the Major League game Friday, with Kaprielian to follow, but the change of plans (perhaps prompted by the Blackburn news) gave both the opportunity to up their workloads for the day. Sears pitched in a "B" game.

“You’ll see guys over there getting their innings and getting their pitch count as well,” Kotsay of upcoming "B" game usage. “The Paul situation shows its head, and thankfully we will have guys built up that can step in.”

Kyle Muller is scheduled to start Saturday’s home game against Cincinnati. Shintaro Fujinami will start against the Los Angeles Dodgers at Camelback Ranch on Sunday, with Drew Rucinski scheduled to piggy-back. But as the A’s look to stretch out their pitching staff, one of those two may start a "B" game instead.

Based on the number of Spring Training games remaining until the start of the regular season, Fujinami and Rucinski are best lined up to start Opening Day, although there is still time to juggle appearances to set the rotation in a number of ways.

“Whoever gets that ball that day, we are going to go out and support him,” Kaprielian said “It’s obviously special to get that nod. Whoever it is, we’ll be happy for him. The only thing any of us can do is continue to go out and pitch and do what we do and continue to evolve and get better.”

Kyle McCann, Yohel Pozo and Tyler Soderstrom are the in-house candidates to serve as Shea Langeliers’ backup while Piña recovers. All are non-roster invitees. Pozo is the only one with Major League experience, hitting .284 with one homer and nine RBIs in 21 games with Texas in 2021.

Soderstom, 21, is the A’s’ No. 1 prospect according to MLB Pipeline, and slashed .267/.324/.501 at three Minor League levels in his first full season in 2022. He was their No.1 draft pick in 2020 and played his final nine games last season at Triple-A Las Vegas.

“Looking at how we view Tyler, I think the development probably outweighs accelerating him to the Major League level, but to say that has been ruled out, it hasn’t,” Kotsay said. “It’s part of a discussion we will have to entertain now that Manny is definitely on the IL.”