KANSAS CITY, Mo. — The Red Sox do not quite understand how and why it’s lingered this long, but Brock Holt still has a concussion more than 2 1/2 half weeks after he collided with Dustin Pedroia in Toronto.

The diagnosis was confirmed by concussion specialist Dr. Michael Collins in Pittsburgh, where Holt visited Thursday before returning to the Sox on Friday.

The team is holding out hope that Holt can return to action before the season ends.

“He’s not cleared to play yet,” Red Sox Manager John Farrell said Friday. “It was confirmed when he saw Dr. Collins in Pittsburgh that he’s dealing with a concussion. To what degree, that’s going to depend on the time needed before he gets back on the field for us, but he’ll go through some exertion testing (yesterday).”

Holt played 10 games after the Aug. 25 collision, then missed time with what the club thought was the flu. But his absence has dragged on for seven games and counting.

“He’s been dealing with a couple of things simultaneously, as we know now with all the examinations in Pittsburgh confirming that he’s dealing with a concussion,” Farrell said.