INDIANAPOLIS, Ind. – The Indianapolis Colts placed Jacoby Brissett in the NFL’s concussion protocol even though their starting quarterback passed two concussion evaluations during and two more after Sunday’s loss to the Pittsburgh Steelers.

Dr. Allen Sills, the league’s chief medical officer, explained in a Tuesday conference call Brissett experienced “some very mild symptoms’’ 20 or 30 minutes after the game despite passing two additional evaluations in the locker room.

“He again was normal neurologically in all the tests,’’ Sills said. “But because there were some very mild symptoms that appeared, and using what I would refer to as precaution, the team decided that at that point they would place him in the concussion protocol and treat him for that diagnosis.’’

“All of our protocols were followed.’’

Brissett suffered a hit to the back of his helmet while being tackled late in the third quarter against the Steelers. He immediately grabbed the back of his helmet and remained on the ground for a few seconds. As team personnel approached, Brissett was helped up and jogged to the sidelines.

He went to the blue medical tent next to the Colts’ bench, was checked for a concussion by team doctors and passed the evaluation. The unaffiliated neurological consultant (UNC) was tending to Colts defensive back Kenny Moore in the locker room at the time for a possible concussion. Once the UNC was available, he evaluated Brissett, who again passed the evaluation.

“(Brissett) had no symptoms, no findings,’’ Sills said. “There was nothing to suggest anything that was abnormal at that point. Based on that, and again, in conjunction with an injury video review, everyone in the equation felt that there was no diagnosis of a concussion.

“The player returned to the game.’’

Sills added the Colts continued to monitor Brissett for the remainder of the game, looking for possible signs of a concussion. He was given another evaluation once he returned to the locker room, which he passed.

However, Sills said, “at some point, 20 to 30 minutes after the game, it felt like there might be the emergence of some very mild symptoms.’’

Brissett again was evaluated for a concussion. Even though he passed that evaluation as well, the Colts decided to enter him into the league’s concussion protocol “out of an abundance of caution,’’ according to Sills.

Geathers activated

Clayton Geathers has been added to the active roster from the reserve/physically unable to perform list. The veteran safety recently returned to practice after undergoing surgery in March to repair a bulging disc in his neck.

Geathers, a 2015 fourth-round draft pick, suffered the injury while tackling Tennessee Titans’ running back DeMarco Murray Nov. 20.

In three seasons, Geathers has appeared in 24 games, 11 as a starter.