Cincinnati Reds manager Dusty Baker underwent another test Thursday and will remain hospitalized at least one more day so doctors can monitor his progress after he was diagnosed with an irregular heartbeat.

If all goes well, Baker could return to Cincinnati on Friday, the team said.

General manager Walt Jocketty visited Baker in the hospital Thursday morning and reported that the veteran manager was feeling good.

Bench coach Chris Speier served as acting manager for a second straight game as the Reds went for a sweep of the Chicago Cubs, a victory that would clinch at least a wild card spot. Cincinnati's magic number for winning the National League Central is three.

"I worry about Dusty and everybody in that clubhouse was really worried last night," Speier said. "You don't just go to the hospital for a cold or anything like that. And I still feel that way. … My thoughts are more about Dusty than this game."

Baker left Wrigley Field in street clothes more than two hours before Wednesday night's game, and it was initially announced he would have chest X-rays to "rule out pneumonia."

The 63-year-old Baker managed his 3,000th career game Tuesday night against Chicago. He has also managed the Cubs and Giants.

Speier said he saw no warning signs that Baker was not feeling well.

"I think everybody at this time of year, everybody is a little beat up, everybody is a little tired," Speier said. "He's done it for so long. He's a little bit used to it, but I was thinking about it last night: 'Wow, he's done this for 3,000 games."'

The Reds had a magic number of three before the finale against the Cubs as they seek their second NL Central title in three years.

Cubs first-year manager Dale Sveum said the job is demanding.

"Whatever health issues we all have, you never take your health for granted," Sveum said. "All our wishes and all our prayers and everything go out. Hopefully, everything's good with Dusty because he's a great guy and the rest of this year is going to be very important for him to be around and healthy."