SAN DIEGO - Had things been different, had a pristine opportunity not been squandered on a perfect day, Jared Allen would have been more expansive.

He had a lot to talk about. His six tackles, tops among Vikings defensive linemen. His half-sack. His surprisingly fluid interception while dropping in coverage that, at the time, appeared to be a key moment in a road upset.

Afterward, though, he was just upset -- period.

"Big plays are fun to make," he said. "And we'd be sitting here laughing about it. But, instead, we're going to talk about how we didn't do enough to win."

Bashing the Vikings' somnambulate offense was the obvious move after Sunday's come-from-ahead loss to the Chargers at Qualcomm Stadium. But let the defense get in on this action, too. The Chargers scored on three of four possessions in the second half before finally running the clock out on their fifth second-half drive. Those were scoring drives of seven, nine and six plays. San Diego held the ball for nearly 21 of 30 minutes in the second half as the Vikings tackling deteriorated and costly penalties rose.

None of that is a laughing matter.

"That can't happen," cornerback Antoine Winfield said. "We simply didn't accomplish our task. We didn't get off the field. We didn't help our offense."

Clearly, the Vikings offense wasn't helping the cause either. But the Vikings defense managed to get decent pressure in a first half that ended with the Vikings leading 17-7. The only Chargers score came after an interception that gave them the ball on the Minnesota 6-yard line. Other than that? The Vikings defense forced three punts, got the ball back on downs when the Chargers were forced to go for it on fourth down with their placekicker injured. The final drive of the first half ended in Vikings territory when Brian Robison got his hand on Philip Rivers' arm, forcing the Chargers quarterback to toss a floater that Winfield intercepted.

The second half was a different story. Starting with the second half's first possession, the Chargers started finding their offensive rhythm, and the Vikings began struggling with their tackling. The first TD drive was keyed by a 37-yard catch-and-run out of the backfield by Mike Tolbert. It was the first of many times the Vikings allowed San Diego to turn a back out of the backfield or a receiver running a shallow crossing route from a short gain into a big play.

"That was the problem, the leak-out," Winfield said. "The quarterback would find him, and then we'd miss tackles."

Down three, San Diego drove from its 23 to a third-and-3 at the Vikings 24 when Allen, dropping into coverage as part of a blitz package, made a pretty interception of a pass to running back Ryan Mathews and returned it 14 yards. It was his fifth career interception, his fourth with the Vikings, tying a team record.

"If I'd had a little more speed or jukes, maybe I could have done something better with it," Allen said.

That was the last time the Chargers were stopped.

"We have to do a better job of getting off the field in key situations," Vikings coach Leslie Frazier said. "It's hard to play good defense when you don't tackle, or don't tackle well."

With the score tied 17-17, San Diego's go-ahead touchdown drive was kick-started by cornerback Cedric Griffin's unnecessary roughness call and finished with a 19-yard catch by Tolbert. Desperate to get the ball back late, the Vikings defense was short-circuited by penalties.

"We blew it, man," Allen said. "We gave the game away. We just gave them the end of the game."