GLENDALE, ARIZ. - We can be assured there were long discussions Sunday among Vikings fans on the improved play of quarterback Tarvaris Jackson.

The reviews were positive after Jackson's victorious second half in Detroit a week earlier. On Sunday, he threw four touchdown passes in a road victory over Arizona, the already-crowned champions of the woeful NFC West.

This quarterback is much improved over the starter we saw in two early losses. And one large reason is that he's now quarterbacking a much improved team.

The Vikings of early September were a shaky unit across the offensive front and underwhelming on the defensive front. The Vikings receivers weren't getting as much separation as opposing receivers were getting against the Vikings secondary. The special teams were unimpressive covering and returning.

Even after veteran Gus Frerotte replaced Jackson at quarterback, you kept looking at the Purple and saying: "They just aren't that good."

That has changed -- and there couldn't be a better time for the transformation to become clearly obvious than in December.

The Vikings pushed their winning streak to four with a dominating 35-14 victory over Arizona. They are 9-3 going back to a victory over Carolina on Sept. 21.

There were a couple of clinkers after that, of course -- particularly a loss at Tampa Bay on Nov. 16. The winning streak started a week later with an easy victory at Jacksonville.

Does this team's strong play go back to that game?

"I think it was a while before that," right tackle Ryan Cook said. "We let the Tampa game get away in the second half, but we didn't feel like it was a case of being beaten physically."

Wherever you want to trace the turnaround to the start of this winning streak or way back to the Oct. 6 victory in New Orleans (8-2 starting then), you might be hard-pressed to find an NFC team more physical than the Vikings at this moment.

There are many reasons for this -- and they start with Adrian Peterson.

The Vikings jumped on Arizona for three touchdowns in the first 12:17 -- the first on a Bernard Berrian punt return, then two scores following turnovers.

After that, the Vikings gave the Cardinals a faceful of Peterson, with some Chester Taylor for good measure. By the middle of the second quarter, the Arizona defenders were walking around with heads hanging.

Peterson finished with 28 carries for 165 yards. That gave him the Vikings' single-season record at 1,581 yards -- 60 more than Robert Smith in 2000. Taylor added 66 yards on 10 carries, and also scored untouched on an 11-yard dump-off by Jackson to make it 28-0 at halftime.

"That's the easiest touchdown I've scored in my life," Taylor said.

It came at the end of an official 91-yard drive. The Vikings also overcame three false starts, making it 106 yards, with the first 95 on runs by Peterson and Taylor.

"It all starts with the guys up front," Peterson said. "It takes a lot of willpower to move the line of scrimmage. We could've put Fahu [Tahi, the Vikings fullback] back there and he would have been able to pick up yards."

Asked about breaking Smith's record, Peterson said: "It means a lot. But the guys up front ... and to get the win. It trumps [the record] to get the win."

Peterson found much of his room on the left edge. "Yeah, we have Big Mac [Bryant McKinnie] over there knocking down people," he said. "When he gets that corner, it's pretty open."

Arizona had the fifth pick in the 2007 draft. The Cardinals took offensive tackle Levi Brown over Peterson. Brown had a tough day, including taking a pratfall on the warning track as he tried to hand his gloves to a young fan while leaving the field.

Would the Cardinals like a do-over on the '07 draft?

"I don't know," Peterson said. "Maybe you should ask those guys how they feel about it."

Antonio Smith, a Cardinals defensive end, gave a hint as to how he might feel about the decision. Asked how much impact the threat of Peterson had on other Vikings hauling in four TD passes, Smith said:

"To be perfectly honest, I think everything that is good about that team is that boy. He makes that team a lot better than what you look at on film."

Patrick Reusse can be heard weekdays on AM-1500 KSTP at 6:45 and 7:45 a.m. and 4:40 p.m. • preusse@startribune.com