"This is something you don't want to fool around with," manager Jim Leyland said.
Avila did not accompany the team to Chicago; instead, he's expected to return home to Detroit for further examination. Bryan Holaday will be recalled from Triple-A Toledo prior to Monday's series opener against the White Sox.
Avila was briefly hospitalized in Cleveland on Thursday and went to Detroit that night after leaving Thursday's game with nausea and light-headedness. A CT scan taken in Cleveland came back normal, the Tigers said, and team doctors cleared him to play on Friday after he passed a series of tests for a possible concussion. Avila said at the time that he wouldn't cheat the test, having gone through a scare last September in a collision with Prince Fielder while chasing a foul ball.
"Trust me -- the reason why I'm here is I have absolutely no doubt in my mind that I'm physically and mentally capable of playing," Avila said on Friday.
Avila didn't on play Friday, but he started behind the plate on Saturday.
Symptoms of a concussion can reportedly occur or reappear hours or days after an injury. Tigers slugger Miguel Cabrera sat next to Avila in the visitors' clubhouse during the series in the Bronx and said he didn't notice anything when Avila walked in.
"You have to worry," Cabrera said, "because that's dangerous."
The Tigers had optional batting practice on the field on Sunday morning, but Avila didn't take part. He spent the afternoon at the park, but the Tigers' medical staff had him lie down in the training room during the game. Starting pitcher Justin Verlander, whom Avila was originally scheduled to catch, said he saw Avila in the training room after he left the game.
"That was one of the first things I did, was walk in and ask him how he's feeling," Verlander said. "He said he feels a lot better now, but he told me he was going to go on the DL. Obviously, when you get into a situation with a concussion, personal safety and personal health is the first thing you need to take care of."
The assuring answer from Avila did not diminish any concern.
"Obviously, I'm concerned for him," Verlander said. "I think I'm more concerned personally for him. I'm just really glad the game that he caught [Saturday], he didn't take one of those patented Alex Avila foul tips right off the facemask. He was able to answer all the questions and he passed his tests, so that's why he was in the ballgame, but I guess he had some symptoms pop up today."
That concern was universal in the visitors' clubhouse. Many who have played with Avila for a while say he takes more foul tips than any catcher they've seen.
"You guys have seen him," Verlander said. "He's taken a beating. He has. Seven days could be really good."
Victor Martinez, who split catching duties with Avila in 2011 before Martinez's knee injuries made him Detroit's full-time designated hitter down the stretch, seemed particularly concerned.
"I have never been with somebody who gets hit as Alex does, man," Martinez said. "It's amazing. He just … it's not good, man. It's tough."