In a game that Vikings coach Leslie Frazier said was designed to be a tune-up for the first regular-season game, the starters played through the first series in the second half, and the coach can’t be happy with what he saw in the 12-10 loss to the San Diego Chargers.

The Vikings offense didn't look ready to play and stumbled out of the gate, and QB Christian Ponder said that "set the tone."

“We never really got in a rhythm,” Ponder said. “When we get the ball first in a game, it’s really important for us to set a tone. Not only did we go three-and-out on the first drive but on the second as well.”

For a unit that had put itself in scoring position in all five previous preseason opportunities, the first-string offense had as many points (3) as they had turnovers and looked anemic in all the series except its last, which ended on the 4-yard line thanks to a fumble by FB Matt Asiata.

The defense, on the other hand, shut down the Chargers, but San Diego was missing 18 players before kickoff, including QB Philip Rivers, TE Antonio Gates and RB Ryan Mathews (who had been injured earlier in the preseason). The Chargers' offense was clearly undermanned and managed to put up only six points against the Vikings -- but DE Jared Allen said the defense did its job.

“We did what we were supposed to do tonight,” he said. “They had a lot of their young guys playing because they were a little beat up, and if you are going against backups, you should dominate -- and we did. We held them to no touchdowns. We held them to 45 yards rushing in the first half. Minus the one 15-play drive (we gave up), I thought everything else was pretty good.”

The Viking took the lead momentarily late in the game, but the defense couldn’t stop the Chargers, who marched into position for a game-winning 45-yard field goal.

Ponder’s travails: As good as Ponder looked in the first two preseason games, he looked that bad against the Chargers. He was 9 of 16 passing for 115 yards, one pick and a 52.9 rating. He appeared out of sync with his receivers and his offensive line, which gave up five sacks in the game. The line struggled with a good Chargers front seven, but Ponder took it on himself.

“I think I got myself in trouble,” he said. “I was getting back on the top of my drop and kind of just sitting there. And that puts a lot of pressure on our tackles. I need to do a lot better job of stepping up and moving forward. I’ve got to do a better job of finding windows to find guys. It’s on me. I have to get better in the pocket, and usually I don’t do that. I don’t know why it happened in this game, but it’s something to work on at practice and get better at.”

Sage to the rescue: QB Sage Rosenfels solidified his spot on the team (if it was ever in question) by nearly winning the game with a 10-play, 62-yard drive in which he went 6 of 6 for 51 yards and threw a 1-yard TD pass to Asiata. The score put the Vikings up for the first time in the game with 1:50 remaining. The drive came against a Chargers defense that was deep into its reserves, but Rosenfels demonstrated his command of the Vikings offense as he quickly moved the team downfield for the lead.

Brinkley inspires: Earlier in the week, Frazier said he wanted to see a good game out of LB Jasper Brinkley, and he got it. Brinkley played aggressively and with more confidence than he had in the first two games, collecting four solo tackles, two for a loss, two sacks and three quarterback hits.

“Jasper seemed like he played a lot better,” Frazier said. “He was more aggressive, he seemed like he was out there having fun. He let it go a little bit. It was encouraging, his play. He made a lot of plays tonight, so that should help his confidence, which, in turn, should help our defense. That was inspiring to see him play as aggressively as he did.”

Back to the trainer’s room for Robison: CB Josh Robinson returned from his hamstring injury last week, played well against the Bills and took many first-team reps Friday against the Chargers. He had an up-and-down performance until he made a big stop on a third-down pass play -- but it was his last. Robinson suffered a concussion and left the game before halftime. Frazier said he would learn more about it as the week goes on.

More injury news: S Mistral Raymond experienced lower back pain and tightening in pregame and did not suit up. ... TE Rhett Ellison got hit on the knee in the ballgame. Frazier said he would learn more after an MRI. ... CB Marcus Sherels and S Andrew Sendejo each sprained an ankle. After the game, Frazier said he wasn't sure of the severity of either injury.

DB Eric Frampton hurt his groin and missed time in the game.

For more Vikings news and notes, follow Joe Oberle on Twitter @CBSSportsNFLMIN.