Byron Buxton experienced a mild headache Saturday morning, one day after being hit in the helmet by a 91-mph fastball. That’s a possible symptom of a concussion, so he won’t play again until he is symptom-free.

But given how minor the problem is, the Twins believe their center fielder will be cleared to play when the playoffs open Tuesday.

“We’re optimistic about that,” said Derek Falvey, the Twins’ president of baseball operations. “The symptoms check off as mild. There’s a set of checkpoints you look at, and he has only a few of them that are consistent with a mild concussion. He’s got to get down to zero of those symptoms.”

The Twins clearly consider themselves lucky that Buxton, who has missed playing time because of concussions twice before in his professional career, wasn’t more seriously hurt by the pitch from Reds reliever Lucas Sims, who appeared shaken on the mound as Buxton laid in the dirt.

“Everyone was very eager to see how Buck was doing today. It’s no secret how important Buck is, and what an excellent player he is, and how meaningful he is to our group,” manager Rocco Baldelli said. “We’re going to remain in that frame of mind, and according to what we found out today, that’s where we should be.”

The news was even better for Josh Donaldson, who came out of the game after the right calf, which kept him out of action for all of August, cramped up while batting Friday.

“J.D. walked into my office and said, ‘Hey, I woke up feeling pretty good. I’m walking around and feel all right,” Baldelli said. Donaldson also sat out Saturday, but is expected back Tuesday.

Arraez activated

When Ehire Adrianza replaced Donaldson in the second inning on Friday, the Twins were left without an infielder on the bench, a bit of exposure “that’s happened a little more this year than a normal year,” Baldelli said. But the team addressed it Saturday by activating Luis Arraez, who hadn’t played since Sept. 8.

Arraez might not be completely healed from a nagging knee injury that caused him to go on the injured list, and a sprained ankle he suffered while preparing to return, but “he moved around pretty well [Friday], and he’s been hitting every day,” Falvey said. “When we told him he was activated, he was excited. He’s ready to get into the lineup.”

To make room for Arraez, outfielder LaMonte Wade Jr. was optioned back to their taxi squad.

Colina sent back

Edwar Colina’s dream-turned-nightmare Friday got a little worse, when the Twins returned him to their taxi squad after one day — and one awful debut — in the major leagues.

The 23-year-old Venezuelan, allowed the first six batters he faced to reach base, including a home run to Mike Moustakas on his second pitch. When he finally recorded an out, a fielder’s choice in which a runner was forced out at the plate, Baldelli removed the rookie righthander, who had allowed three runs, four hits and two walks, and owned an 81.00 ERA.

The debut ranked with that of former Twins Travis Miller, who in 1996 gave up seven runs in a start that lasted one inning, or J.T. Chargois, who four years ago allowed five runs in two-thirds of an inning in his first game.

A day later, Colina was gone, with righthander Devin Smeltzer recalled.

Cameras caught Rich Hill, the Twins’ oldest player, giving a distraught Colina a pep talk on the bench, and Baldelli said he assured Colina that nothing about it changed the Twins’ opinion of him.

“He’s a guy who has a very bright future, and a guy that we’re going to be relying on in the future to get very important outs at very important times. It’s still an important day in his career to get out there and become a big-leaguer and go do his thing out on the mound,” Baldelli said. “And overall, once we get a little bit further into the future, and the emotion of it dies down a little bit, he’s got a lot to be proud of.”