CINCINNATI – Bengals defensive tackle Geno Atkins, maybe Mike Zimmer's greatest find during his Cincinnati days, darted between the center and a guard to push the pocket.

That quick pressure forced Vikings quarterback Teddy Bridgewater to flee to his left, directly into the reach of Bengals defensive end Margus Hunt, who had slipped out of left tackle Matt Kalil's block.

Shouts of "saaaaaaaaack!" and a quick whistle spared the quarterback any punishment.

That was one of a pair of would-be sacks the Vikings' pass protectors surrendered in their three intersquad practice periods on Thursday morning — an improvement from Wednesday but still substandard for this reshuffled and reshuffled and reshuffled offensive line.

"They've got a pretty good defensive line. We're continuing to progress," Zimmer said after the practice. "We did some good things, and there's some things we have to work on."

Two weeks after the Vikings took the field in Mankato and following two joint practices with the Bengals outside Paul Brown Stadium, there remains plenty to work on and not much clarity with an offensive line that will be under the microscope in Friday night's preseason opener.

Vikings coach Mike Zimmer watched one of his offensive linemen block during a joint practice with the Cincinnati Bengals on Wednesday.

The good news is the Vikings still have a month to choose five starters before the games count.

Barring an injury before Week 1, the left side of the starting offensive line will be Kalil at tackle and Alex Boone at guard, as has been expected all along. While Zimmer had made nothing official, Andre Smith clearly will be the starting right tackle after manning that spot capably in both of this week's practices against his former team.

But who starts at center and right guard? Zimmer wants to make sure he gets that right.

On Wednesday, Joe Berger got most of the first-team reps at center with John Sullivan subbing in. Brandon Fusco was as right guard. But on Thursday, Berger was forced to slide over to right guard with Fusco, who has been dealing with injury, not practicing.

Zimmer would not say whether Fusco will suit up against the Bengals on Friday night. He also would not disclose who starts at center if Fusco does. And could Berger theoretically compete with Fusco for the starting gig at right guard? Yeah, Zimmer wasn't going there either.

"We'll keep going. We'll keep looking," Zimmer said. "We're going to probably move a few [offensive linemen] around next week and look at some other combinations."

Zimmer reluctantly conceded that the retirement of right tackle Phil Loadholt and the mystery illness sidelining right guard Mike Harris prevented the Vikings from seeing the fierce caliber of training camp competition they had tried to set up at those two positions.

"I guess so," Zimmer said, adding, "I'm happy with our guys. I like the way they work."

During Wednesday's steamy afternoon session, the first-string offensive line was inconsistent as the Bengals got penetration several times. On one particularly ugly rep, blitzing Bengals linebacker Vontaze Burfict knocked Sullivan on his back on his way to Bridgewater. But on other plays they protected Bridgewater long enough for him to produce big-gainers.

Bridgewater had their backs when a reporter suggested his linemen had an uneven day.

"I didn't feel like they were up and down. I think those guys are doing a great job of adjusting to different looks that we haven't seen," the third-year QB said Thursday. "[New offensive line coach Tony] Sparano challenges those guys. He pushes those guys. We're going to have a great room. ... Those guys want to be the best at what they do."

"Those guys" looked a little better Thursday. Other than Hunt's sack, the only would-be Teddy takedown came on a fourth-and-10 play when the Bengals sent several defenders.

Two days of padded practices against a good Bengals front seven were more beneficial for the first-string offensive line than a handful of snaps in Friday's preseason opener will be. But their play in those televised preseason snaps is going to be magnified, of course.

A clean game in pass protection will quiet their skeptics for a few days. But questions will likely remain and they will definitely have plenty more to work on back at Winter Park.