MESA, Ariz. — Just going by the pitching schedule, it’s fairly easy to see how the A’s rotation will shake out.

In order right now, it’s Kendall Graveman, Sean Manaea and Jharel Cotton — already announced as the 1-2-3 starters — followed by Andrew Triggs and Raul Alcantara.

The clear odd man out: Jesse Hahn ’s schedule doesn’t coincide with the rest of the A’s starters, and Saturday he was starting a split-squad game on the road against the Dodgers on the same day Manaea was working the home game against Cincinnati.

Then there were Saturday’s results. Hahn allowed eight hits and seven runs, five earned, in 31/3 innings, and his ERA is 8.80. So even if things hadn’t already been decided (as the schedule indicates), Hahn’s outing would be enough to take him out of the running.

Hahn was Oakland’s No. 3 starter the first half of 2015 before incurring a forearm strain. Healthy last season, he never regained his early 2015 form and had an ERA of 6.04 in nine starts with the A’s. He was 1-7 with a 4.32 ERA at Triple-A Nashville.

Billy Beane, vice president of baseball operations, identified Triggs as a rotation candidate at the end of last season, while Alcantara is out of options.

Detwiler’s decision: Left-hander Ross Detwiler has an opt-out in his contract for Sunday and is expected to exercise it because he is not going to be on the Opening Night roster. Detwiler has an 11.88 ERA in eight games.

“The way the last couple of games went, I can guess,” he said Saturday.

It’s unclear if there is interest in him elsewhere. Detwiler is on the schedule to pitch in the A’s game against the Brewers on Sunday.

Briefly: Shortstop Marcus Semien was sent home sick. … Khris Davis (quadriceps) and Jaff Decker (oblique) will get at-bats in a minor-league game Sunday.

Susan Slusser is a San Francisco Chronicle staff writer.

Reds 11, A’s 6; Dodgers 11, A’s 6

Notable: Starter Sean Manaea gave up six runs in the second against the Reds, five earned, including two via bases-loaded walks. … Manaea left after the third inning and finished up with 10 pitches in the bullpen to get in his full workload. … Sean Doolittle gave up three hits and two runs in his inning of work. … Rajai Davis hit his first homer of the spring. .. Trevor Plouffe had two hits and is batting .425; he left after feeling a minor tweak in a hip muscle. ... At Camelback Ranch against the Dodgers, Lazarito Armenteros, 17, became the youngest A’s player to appear in a Cactus League game when he flied out to center in the eighth. He popped to short in the ninth. … Simon Castro, unscored upon in his first eight games, allowed three runs in 11/3 innings.

Quotable: “Just trying to nibble on the corners too much. I finally just said ‘I’m going to throw it right down the middle and let them hit it,’ and got good results.” — Manaea, who settled down in the third after walking five in the second inning.

Sunday: A’s at Brewers in Maryvale, Ariz., 1:05 p.m. Radio: 98.5 FM.

— Susan Slusser