MESA, Ariz. -- With Opening Day on the horizon, the Athletics have decided on which five starting pitchers will begin the season in the rotation.

While the order outside of Opening Day starter Luis Severino could still be adjusted, manager Mark Kotsay confirmed Wednesday morning before the A’s took on the Guardians at Goodyear Ballpark that the five-man rotation will consist of Severino, Jeffrey Springs, Osvaldo Bido, JP Sears and Joey Estes.

The reveal settles what was a tight battle for the final rotation slot between Estes and fellow right-hander Mitch Spence, who will enter the season in the bullpen.

“It was a difficult decision,” Kotsay said. “But [it's] one that I feel confident in based on Spence’s ability to pitch out of the bullpen in various roles and really impact our club’s success.”

Estes holds a 4.63 ERA with eight strikeouts and one walk in 11 2/3 innings through four Cactus League starts. Spence, meanwhile, carries a 6.17 ERA in four spring outings, though that number was severely inflated by his most recent outing on Saturday against the Brewers, which saw him allow seven runs on seven hits and a walk in 3 2/3 innings. Prior to that, Spence had allowed just one earned run with seven strikeouts and two walks in 10 innings.

A large reason why Spence will work out of the bullpen is his success doing so last year. The first overall selection in the 2023 Rule 5 Draft by the A’s, Spence successfully spent the entire 2024 season with the A’s -- and fared well in multiple roles. After starting out in the bullpen, injuries to others created a spot for him in the rotation, which he grabbed and never looked back. Overall, he posted a 4.58 ERA in 35 games (24 starts) with 126 strikeouts over 151 1/3 innings.

This spring, Spence has seen an increase in his fastball velocity, consistently sitting 95-96 mph during his outings after it averaged 91.9 mph last season. He credits the uptick to the work he put in this offseason, which included strength training and going to physical therapy three times per week.

“My arm, in general, is a little bit stronger,” Spence said. “I was also really working on throwing my fastball more efficiently. I used to cut the fastball a lot. Now, getting behind it a little more, the force is going into the ball instead of cutting it. Instead of throwing it more like a slider, now it’s more of a true cutter.”

With that improved cutter, along with a slider that performed as one of the better pitches in baseball last season and a sinker Spence focused on this offseason, Kotsay said he views the righty as more than just a long reliever.

“We’ve got a lot of confidence in Spence,” Kotsay said. “You could see him in a long role, but you could also see him in a high-leverage role. He’s had that experience down there in the bullpen.”

Kotsay also emphasized that just because Spence will join the bullpen for Opening Day, it is more likely than not that he -- and others who will not make the roster out of Spring Training such as J.T. Ginn, Brady Basso and Gunnar Hoglund -- will make starts for the A’s at some point during the season.

“We’re starting this way, but that doesn’t mean that we’re going to finish this way,” Kotsay said. “Something could happen in the first few weeks to change that. But we feel confident in the way we’re going to break camp.”

Gelof finishing strong
Good Spring Training numbers are not guaranteed to translate into the regular season, but the A’s are hopeful that Zack Gelof is peaking at the right time.

Entering Wednesday’s game, Gelof was 7-for-17 (.412) with a home run over his past seven games. More importantly, he had struck out just three times in 20 plate appearances, showing signs that his goal of cutting down on punchouts -- he led all American League hitters with 188 strikeouts in 2024 -- is coming along well.

“He and [director of hitting Darren Bush] have worked really hard this Spring Training,” Kotsay said. “The adjustments that he’s made -- and are still being made -- we feel are going to put him in the best position to have success. I think he’s believing in that, and we’re seeing some results, which is always a good sign for a player’s confidence.”