Five takeaways from the Vikings' 3-0 start in the preseason

The Vikings are a perfect 3-0 in the preseason, but there still is plenty we don't know about Mike Zimmer's team with the season opener against the St. Louis Rams now less than two weeks away.

Who is the quarterback? Who will start at safety and middle linebacker? And are these guys actually for real?

We have learned some things about the Vikings, though, in their preseason wins over the Oakland Raiders, Arizona Cardinals and Kansas City Chiefs. These are five of the biggest takeaways.

Zimmer was widely praised for hiring offensive coordinator Norv Turner to serve essentially as the head coach of his offense. Turner is regarded as one of the savviest play-callers in the league, and wideouts, tight ends and running backs have all seemingly put up big numbers at each of his stops.

Second-year wide receiver Cordarrelle Patterson and towering tight end Kyle Rudolph both look poised to have productive seasons — each has scored on a long touchdown reception during the preseason — and if Adrian Peterson's backups are averaging 4.3 yards per carry, you have to figure the perennial Pro Bowl back will be able to break into space once the regular season rolls around.

And then there are the quarterbacks. Matt Cassel and Teddy Bridgewater have each completed at least 65 percent of their passes. Bridgewater has thrown four touchdown passes with no interceptions and Cassel has averaged an impressive 9.4 yards per attempt.

The Vikings have three building blocks in the secondary in safety Harrison Smith and cornerbacks Xavier Rhodes and Captain Munnerlyn. They also have more question marks there than anywhere else. They still haven't picked a second starting safety, Josh Robinson looks like he will be tabbed to be the team's third cornerback by default and the Vikings lack quality depth in the secondary.

It is encouraging that the Vikings are allowing just 5.8 yards per pass attempt during the preseason.

Of course, the secondary's job will be made a lot less difficult if the Vikings can get after the quarterback like they did against the Chiefs. They racked up five sacks in the win, and after the game, Zimmer lamented the few times they let quarterback Alex Smith wiggle out of their grasp.

The Vikings allowed defensive end Jared Allen, who had 85½ sacks in six seasons here, to walk in part because Zimmer believed he could help Everson Griffen, Allen's younger successor, become a star.

But Griffen won't have to do it alone. Top pick Anthony Barr has showed promise with 1½ sacks in the preseason, and eight Vikings defenders have recorded at least half a sack through three games. Credit Zimmer's clever blitz package and improved execution from the defense for that stat.

The Vikings had perhaps the NFL's most productive overall return game in 2013, with Patterson leading the league with an average of 32.4 yards per kickoff return and Marcus Sherels ranking second at 15.2 yards per punt return.

The Vikings have surrendered 10 sacks during the preseason. All three they allowed against the Chiefs came with the starters in, and Cassel also endured a hard hit when a Chiefs defender drove him into the ground while he chucked up a deep ball to Rudolph during the third quarter. With Cassel on the run, the first-teamers didn't muster much offense after their opening drive.

Zimmer still hasn't named his starting quarterback — a trail of tea leaves from TCF Bank Stadium to Kansas City to St. Louis suggests that it will be Cassel — but regardless of who is under center this season, the offensive line must pass protect better to give the quarterback a chance to thrive.