Heading into Sunday's game against the Chiefs, here are four questions we're trying to answer.

-- Still winless heading into October, do the Vikings have the mental fortitude to bounce back?
At least on the surface, the mood throughout the team is notably upbeat. Following Thursday afternoon's practice, head coach Leslie Frazier lauded his team's energy and focus. On Friday, it was more of the same.

"We feel like we're so close," Frazier said. "And if we can put a good four quarters together and boost our confidence, we can get on a roll. We need to do that."

It's not just the head coach who's feeling the positive vibes. Defensive tackle Kevin Williams said Friday that he too has been impressed by the team's enthusiasm this week.

"You hear people say, 'Whistle while you work,'" Williams said. "That's us. We're out there working away, getting the game plan in and taking care of our business. There's no down mood around here. Clearly, we've dominated teams right off the bat in games this year. The end results haven't been what we like. But we know we're better than the teams we've played. It all starts with believing that."

Given Kansas City's injury difficulties, the Vikings seem to be the better team this week; the oddsmakers have them as two-point favorites. We'll see if that translates into more whistling Sunday evening.

-- What's wrong with Bernard Berrian?
You all know the stat line: three games, one catch, 17 yards, endless criticism. As the outside world attempts to solve the "What's wrong with Bernard Berrian?" riddle, I asked the eighth-year wide receiver for a self-diagnosis Friday afternoon.

"I've been doing the same things I've always been doing," Berrian said. "I've been getting open. It's just that we haven't been able to connect. I'm doing all I can do, really."

Berrian said he sees holes in the Chiefs' run defense that should allow running back Adrian Peterson to get off to a fast start Sunday. And if that happens, the Vikings should have greater opportunity to attack vertically in the passing game.

But will Berrian be able to break out of his funk? It's hard to say. For now, he seems a bit annoyed by all the outside criticism.

"In some ways, it's getting easier and easier to deal with," he said. "I hate to say this. But it's almost like you get used to [the criticism]. Look, I can only control what I can do. And I can't let myself get stressed out over things that I can't control."

-- Defensively, will the Vikings have the discipline and game plan to contain Kansas City running back Dexter McCluster?
McCluster's a unique talent, a running back-receiver hybrid who has the speed to get loose every time he touches the ball. So far in 2011, his stats have been decent at best – 21 carries for 138 yards, 14 catches for 40 yards. But with Jamaal Charles done for the season in Kansas City, the Chiefs are hoping to make McCluster a much bigger part of their offense.

The Vikings know they must keep an eye on the small but shifty second-year back from Ole Miss.

"You never know where he's going to get the ball," Williams said. "He might be in the backfield. He might be in as a wingback. He might get it as a wide receiver. Hell, we might even seen him on defense. But they're going to try to get him that ball. And we understand he's a unique guy once he gets it."

Added linebacker E.J. Henderson: "When he gets in space, he can be dangerous. The biggest thing for us is understanding that it may take a bunch of to tackle to him. And I think we have a pretty good game plan in to account for him."

For the record, the Vikings currently rank fourth in the NFL against the run, allowing just 67.3 rushing yards per game. But keep in mind, three games is a small sample size. And don't forget that the Vikings' strong first halves have also forced opponents to play catch-up through the air.

Still, the ability to limit McCluster on Sunday could prove huge.

-- Who's worse after halftime?
The Vikings' second-half struggles have been well documented this season. The team is still looking for its first touchdown after halftime, having been outscored 67-6 in the second halves of three losses. But the Chiefs haven't been much better. In the season opener, they were outscored 21-0 after halftime by Buffalo. The following week, Detroit put a 28-0 second-half whooping on Kansas City. Last week, the Chiefs outscored San Diego 17-10 in the second half but still lost 20-17.