Leslie Frazier turned his back on a deflated defense and somberly walked the sideline, head down, until he reached the 50-yard line.

The headset was off, and so were the hinges.

Once Tampa Bay running back LeGarrette Blount barreled through the Vikings’ line for a game-sealing, 4-yard touchdown run with 31 seconds left, the Minnesota head coach had license to toss that headset in disgust.

This seemed something far worse. Frazier, like the rest of his team, was still too much in shock to do anything but put his head down and walk.

Sunday’s 24-20 loss to the Bucs left the Vikings 0-2 and out of answers after squandering a second-half lead for the second consecutive week.

Owner Zygi Wilf looked out of answers as he quietly escaped the Vikings’ locker room with a look that begged the question, “What just happened?”

Defensive end Brian Robison looked out of answers when he stared at his cleats for minutes in the locker room, running his hands through his hair in full uniform while teammates hit the showers.

Wide receiver Percy Harvin looked out of answers when he had no choice but to break down the 0-2 start into the purest form.

“You can chop it up any way you can, but we didn’t play for 60 minutes last week or this week,” Harvin said.

The season-opening, 24-17 loss to San Diego was understandable on some levels: The Vikings simply played poorly in the second half.

But on this day, they dominated the first half with a 17-0 lead, didn’t turn the ball over and got a monster performance from Adrian Peterson (120 yards, two touchdowns) – all overshadowed by costly mistakes and the inability to stop Bucs quarterback Josh Freeman late.

Suddenly that 14-year winning streak over Detroit in the Metrodome doesn’t look so safe entering Sunday’s matchup with the 2-0 Lions, who trounced the Chiefs 48-3. Quarterback Donovan McNabb calls the game a “must-win situation.”

The Vikings prepare this week knowing they’ve been outscored by a combined 41-3 in second halves this season.

“It’s going to be a rough week,” linebacker Chad Greenway said.

The theme last week was whether the Vikings will solve their passing woes after McNabb’s 39-yard opener. For the most part, they addressed the problems.

Even with several missed throws, McNabb finished 18 of 30 for 228 yards Sunday and spread the ball to seven different receivers.

As the past two weeks have shown, this team has little margin for error.

Drives to the Bucs’ 11- and 4-yard line resulted in field goals, including a missed throw to a wide-open Visanthe Shiancoe in the end zone on third down.

Eight costly penalties and Freeman picking apart the Vikings’ zone on a 61-yard winning drive left several players resorting to the 60-minute cliche.

No one can relate better than McNabb, who is 8 of 19 for 77 yards in second-half play this season.

“We’ve got to have that attitude that we just can’t be stopped,” McNabb said. “When you have that attitude like that, then you see teams that are 2-0.”

And to think the Bucs punctured a hole in the Vikings’ identity of wanting to get early leads, win up front and control the clock with Peterson.

Then came the two offensive penalties on the first drive of the third quarter.

And then came Robison’s offsides penalty that negated a fumble recovery in the red zone.

And then came Freeman’s (22 of 31, 243 yards) connection with receiver Arrelious Benn for a 25-yard touchdown with 6:39 left as cornerback Cedric Griffin watched in the dust.

This is how a game unravels in the NFL.

The Vikings thought safety Husain Abdullah’s end-zone interception with 7:50 to go in the third quarter would seize momentum after the Bucs recovered an onside kick just a few plays earlier.

But soon enough, the Bucs were cruising through the red zone, and Frazier was preserving his timeouts because he believed his defense would get one last stop.

“We had a three-score lead, thinking we could give it to AP and play good defense,” Frazier said. “We didn’t come out that first series and do the things we needed to do….All of a sudden, they got some energy; things began to turn.”

This is the 11th time the Vikings have started a season 0-2, and just once did one of those teams make the playoffs. The 2008 Vikings finished 10-6 after an 0-2 start.

On the bright side, Pro Bowl defensive tackle Kevin Williams returns to work Sunday after serving a two-game suspension for the StarCaps case.

Maybe the addition of a proven player will help the Vikings avoid sobering statements like this: “We just weren’t good enough,” Greenway said.

Follow Jeremy Fowler at twitter.com/vikingsnow.