MESA, Ariz. -- It looked like a typical Spring Training morning in the Oakland A’s clubhouse on Sunday. Boxes of glazed Krispy Kreme donuts were laid out on a table. Four players were immersed in a card game. Others checked their phones or slowly got dressed.

Typical, perhaps, because the A’s are accustomed to seeing players traded away. Already this spring, they have dealt first baseman Matt Olson, starting pitcher Chris Bassitt and third baseman Matt Chapman. Then on Sunday, Oakland traded starting pitcher Sean Manaea and Minor League right-hander Aaron Holiday to the Padres for right-hander Adrian Martinez and infielder Euribiel Angeles.

Padres get: LHP Sean Manaea, RHP Aaron Holiday
A's get: IF Euribiel Angeles, RHP Adrian Martinez

Neither Martinez nor Angeles has played in a Major League game.

“We’ve gone through this. It’s part of the process,” manager Mark Kotsay said. “You hate to lose someone like [Manaea] this close to the season, but the timing really doesn’t matter. For this group, we’ve gone through it. It’s ‘next man up’ mentality.”

Kotsay named Frankie Montas the starter for the season opener Friday in Philadelphia and said Montas would have been the Opening Day starter even if Manaea hadn’t been traded.

“He’s earned this,” Kotsay said of Montas, who was 13-9 with a 3.37 ERA last season.

Manaea went 11-10 with a 3.91 ERA in 32 starts in 2021 and has posted a winning record in five consecutive seasons. He struck out a career-high 194 batters, which ranked eighth in the American League and eighth in Oakland single-season history.

Manaea tied for the AL lead in starts, ranked fourth in strikeout-to-walk ratio (4.73), sixth in walks per nine innings (2.06), eighth in innings pitched (179 1/3), ninth in opponents’ OPS (.719) and opponents’ on-base percentage (.304) and 10th in ERA, opponents’ slugging (.415) and opponents’ batting average (.255).

Kotsay called Manaea the “heart and soul “of the clubhouse. The left-hander spent his first six MLB seasons in Oakland, with the notable highlight of a no-hitter against the Red Sox in 2018.

"There was a lot of growth," Manaea said. "I came over there when I was 23, and I’m 30 now. So it’s been seven years. There’s been a lot of ups and downs and injuries, and the no-hitter was obviously pretty special. A couple other big games. Just the people that have helped me over there and the opportunity to go through some failure and be able to throw and go through those situations was obviously huge for my development."

“The news this morning hurt a little bit,” pitcher Cole Irvin said. “Sean is an integral part of what it means to be an Oakland A’s player. The energy he brings to the ballpark every day is just unmatched. He is one of the best guys you can have in a clubhouse.

“It will be important to keep our head down and not allow the distractions to hurt us.”

Kotsay said it’s fair to assume that Irvin, who went 10-15 with a 4.24 ERA last season, will slide in as the No. 2 starter behind Montas. Asked about the rest of his starting rotation, Kotsay mentioned Daulton Jefferies, who has pitched in six Major League games and has a 10.45 ERA this spring; Paul Blackburn, who had a 5.87 ERA in nine starts for Oakland last season; and Adam Oller, who had a 2.45 ERA in eight appearances for Triple-A Syracuse in the Mets' system in 2021 after spending most of the year in Double-A. Kotsay said A.J. Puk, who pitched out of relief for Oakland last season, also is a possibility.

“We’ll see where they fall in line,” Kotsay said.

Of the two prospects Oakland received in return for Manaea, Martinez is the closest to appearing in the big leagues. Martinez combined for an 8-5 record and a 3.38 ERA in 26 games, including 22 starts, for Double-A San Antonio and Triple-A El Paso last season. He struck out 122 batters in 125 innings. Martinez, 25, missed the 2016 season following Tommy John surgery and the 2020 season because of the COVID-19 pandemic.

Kotsay said Martinez, who was ranked by MLB Pipeline as the Padres' No. 26 prospect, would begin this season at Triple-A Las Vegas.

“I know he has really good stuff,” Kotsay said. “Obviously, he has an opportunity through this process to impact a Major League team when he’s ready.”

Angeles, 19, was ranked as the Padres’ No. 12 prospect. He hit a combined .329 with 26 doubles, six triples, four home runs, 64 RBIs and 19 stolen bases in 105 games in Low-A and High-A ball last season.

“He has a bright future,” Kotsay said. “His bat-to-ball skills are really good.”

Holiday, 21, was the A’s 13th-round Draft selection in 2021 and went 2-0 with a 0.00 ERA in three relief appearances with the A’s Rookie-level team in the Arizona Complex League last year.

In an odd twist, the A’s played the Padres on Sunday, and it was Manaea’s turn to pitch, so he took the mound against Oakland players who were his teammates just hours earlier.

“I came to the field, and it was a little emotional -- actually very emotional,” Manaea said. “But it was nice to have some closure, and say goodbye to the guys. And then, obviously, pitching against them was a little crazy. … It was just a whirlwind, for sure.”

Manaea tossed 3 2/3 innings of one-run ball and struck out four in Oakland's 8-2 victory. He stopped near the A's dugout on his way off the field for a few more goodbyes and hugs.

“He’s going to leave a big hole to fill,” Irvin said. “But at the same time, we’re the Oakland A’s and we find ways to win ballgames. We have a history of doing that, so we’re going to have that winning mentality every day.

“If you’re not coming to the ballpark ready to win, you’re doing it wrong.”