Joe Mauer’s return from the disabled list might not be as imminent as the Twins had hoped.

The franchise first baseman was “disappointed” by the return of concussion-like symptoms during an early on-field workout Thursday afternoon at Target Field.

“Hitting, I felt pretty good, but taking groundballs and moving around is kind of when I started to feel some of that stuff, so we kind of backed off,” Mauer said. “There’s different levels that we’ve been attacking. Today we got a better feel of where it was at. I’m not there yet.”

Mauer hasn’t played since leaving mid-game on May 18 against the Milwaukee Brewers. He described his condition to reporters after that game as being neck and upper-back related, similar to whiplash, and traced it back to a diving attempt at catching a foul ball on May 11 at the Los Angeles Angels.

On Thursday, Mauer revealed for the first time what happened later that night.

“Obviously, my neck was what it was,” he said. “(On) the drive home, the symptoms started to really kind of pour on. That’s why you didn’t see me for a couple days.”

The Twins placed him on the 10-day disabled list the following day with a cervical strain and concussion-like symptoms. Asked directly if he believes he suffered a concussion against the Angels, Mauer suggested he had.

“Definitely having the symptoms,” he said. “I think that’s kind of how they do (differentiate): If you have the symptoms, then you probably had one.”

It was a Justin Upton foul pop that Mauer chased well down the right-field line during the third inning of a 5-4 comeback win. Angels star Mike Trout was at first base and appeared concerned about Mauer after he returned to his position.

“I remember I came back and kind of walked back gingerly,” Mauer said. “He goes, ‘Are you OK?’ I said, “I’ll probably feel that tomorrow.’ I didn’t think I’d keep feeling it. I was a little messed up there.”

Mauer planned to sit in the dugout during Thursday’s game as another test of his ability to withstand the noise levels associated with a major league game.

“That’s part of it, too,” he said. “Sounds and lights, the whole spiel. It’s a lot noisier around here today than it was the last few days. … I guess we’ll just see how the rest of the day goes, and hopefully it goes well. I’m champing at the bit to get back out there.”

There hasn’t been much talk about activating Mauer as just a designated hitter.

“I’m trying to look at it as coming back and staying once I get here,” he said. “I definitely don’t want to go back into the place I was about a week ago. My goal is to come back and stay.”