Bridgewater is rehabbing daily at the team's practice facility, and Zimmer said the quarterback has "progressed a lot."
"I don't watch him every single day because he's over there off to the side while we're practicing," Zimmer said. "But the reports I get are all positive. And he knows where he's at and where he's got to get to. I think he's progressing well."
On Aug. 30, 2016, Bridgewater dislocated his knee and tore several ligaments, including the ACL, when he went down during a noncontact drill at practice.
The injury ended a 2016 season that had been full of promise. In 2015, Bridgewater had led the Vikings to their first division title since 2009 and had been selected to the Pro Bowl. He led the league in completions in the red zone.
If Bridgewater starts the season on the physically unable to perform list, he would be eligible to come off after six weeks.
When asked what Bridgewater would have to show to be able to come off the PUP list, Zimmer said, "He's got to be able to protect himself on the field and be able to do the movements that are required by his position."
"When he's there, he'll practice," Zimmer added.
Zimmer also talked about the team's move in the aftermath of Bridgewater's injury, trading a first-round pick in 2016 to acquire Sam Bradford from the Eagles. Despite a 5-0 start, the Vikings finished 8-8, third in the NFC North, and missed the playoffs.
Zimmer said he believes the trade for Bradford was a good move.
"I still think the trade was the right trade for us," he said. "Obviously, it was a freak thing that happened with Teddy, but I don't know, I guess you always handle it the best way you can and try to figure it out."
The Vikings will start the season with Bradford, backed up by Case Keenum, who was signed in the offseason. In May, the team declined the fifth-year option on Bridgewater's contract, so he'll be a free agent after the 2017 season.