Mike Zimmer had surgery for torn retina

Vikings coach Mike Zimmer said Wednesday he had surgery to repair a torn retina on Tuesday morning, a day after the team's 20-10 loss in Chicago.

The team said Zimmer underwent a "minor medical procedure." The 60-year-old Vikings coach was back at the team's Winter Park headquarters by the Tuesday afternoon, and announced the procedure at his Wednesday press briefing, during which he was wearing sunglasses.

His procedure came just hours after the Vikings' nationally televised loss to the Bears, marking the second consecutive defeat after a 5-0 start. Zimmer addressed reporters after the game, and the team flew back from Chicago and landed in Minneapolis early Tuesday morning.

In October 2014, Zimmer needed two procedures to remove kidney stones. He has joked with reporters in the past about his knee problems when facing inquiries about injured players.

The Vikings did not trade for offensive line help as the NFL's deadline passed Tuesday afternoon.

A move for a tackle, especially for All-Pro talents such as Cleveland's Joe Thomas or San Francisco's Joe Staley, would've been tough to swing given the Vikings are bumped up against the salary cap. They have less than $500,000 in space and would've needed to trade or adjust contracts to make room. General Manager Rick Spielman noted the Vikings' situation last month.

"I read a lot of things and, you know, it's funny. It's 'we'll trade for this guy or trade for that guy,' " Spielman said. "I think last week we're $50,000 in cap room. I think Rob [Brzezinski, vice president of football operations], with his little magic wand, was able to create some cap room so we can get Jake Long done."

The Vikings traded for quarterback Sam Bradford in September and have $33 million allocated toward players on injured reserve, including running back Adrian Peterson and left tackle Matt Kalil.

Bradford has seen a change in opposing defenses as they've pivoted to stop the pass against what used to be a run-first offense. Subsequently, the ball didn't get out as quickly in losses to the Eagles and Bears, in which Bradford was sacked 11 times.

"When we played Houston, we saw a lot of Cover-1," Bradford said. "We beat it at the line of scrimmage and we beat it quickly. Since then, we haven't seen a lot of Cover-1."

Now defenses are playing with two deep safeties, or Cover-2, which takes away more throwing lanes. And the Vikings' last-ranked rushing attack (2.7 yards per) wasn't able to take advantage in Chicago.

"There are still areas underneath that we can figure out how to get the ball out," Bradford said. "We just got to figure out a way to combat that, because we've seen a lot of it the past two weeks."

First-round pick Laquon Treadwell was active for his fourth NFL game, but the receiver is still looking for his first NFL catch.

Treadwell, suiting up in his hometown Chicago on Monday night, played seven snaps — all on special teams. He nearly blocked a Bears punt. Leading at split end again was receiver Cordarrelle Patterson, a 2013 first-round pick, with three catches in 41 snaps against the Bears.

Treadwell has been on the field for 12 offensive snaps this season, fewest among the six receivers.

• Despite the loss, the Vikings defense is still ranked No. 1 in the NFL (14.9 points per game) through eight weeks of the season. They're also second in yards per play (4.7).

• On offense, the Vikings' 11 touchdowns are second-fewest in the NFL to the Ravens' 10.