SAN DIEGO -- This wasn't exactly what Mike McCarthy had in mind for his debut as an NFL head coach.

The Packers struggled in the opening quarter and never fully recovered Saturday night, dropping a 17-3 decision to the San Diego Chargers in the 2006 preseason opener.

Green Bay had difficulty running the ball, protecting the quarterback and defending third down, and the result was rather predictable given those problems.

"I think we leave here with a sense of reality of how we started our preseason," McCarthy said. "This isn't about me, this is about where we are as a football team. We didn't play the way we're capable of playing. It starts with me. I have to get them better prepared. We made a lot of mistakes, a lot of things were self-inflicted."

Most of those mistakes came in three key areas that will certainly be focused on as training camp continues.

**Running the ball: The debut of the zone-blocking scheme produced just 44 yards rushing, and nearly half (21) were by quarterback Aaron Rodgers on scrambles. The running back quartet of Najeh Davenport, Samkon Gado, Noah Herron and Arliss Beach combined for 14 carries for just 23 yards.

Getting the zone blocking to feel like second nature likely will continue to be a work in progress.

"I never felt a sense of comfort out on the field, and I think that's really important as far as playing offensive line," tackle Mark Tauscher said. "You need a comfort level as far as where you need to get to and how you're going to get there.

"There's really no excuses for it. It comes down to we didn't execute and our tempo wasn't as good as it needed to be. Coaches have stressed the tempo and we weren't up to par tonight."

**Protecting the quarterback: Brett Favre and Rodgers were sacked a combined five times, mostly by blitzing linebackers. A sack in the red zone thwarted the Packers' best chance for a touchdown and led to a field goal.

"We just need to do a lot better job communicating," said Rodgers, who absorbed three sacks but otherwise played well, completing 9 of 11 passes for 124 yards. "We have to be able to pick up those blitzes. We worked on those in practices.

"Obviously they were effective (blitzing), so there's no reason anybody else isn't going to try to light us up."

**Defending third down: The Chargers converted 10 of 16 third downs (63 percent), including eight of nine on two drives that lasted 18 plays apiece and produced 10 points.

"The majority of those things were mental on those third downs," middle linebacker Nick Barnett said. "We clean a couple things up and we get off the field a lot sooner on those 18-play drives.

"Physically I think we can play with anybody, if we clean up those mental errors. We have a lot of young guys and that happens in the preseason. We've got a lot to work on but I still see a lot of potential in our defense."

It was an altogether forgettable night for the Packers' first-string offense, which forced Favre to stay in for much longer than originally planned.

On its first three possessions, Green Bay picked up just one first down, and that came on a defensive penalty. The first and third series each ended 1 yard shy of a first down, while on the second series Favre was sacked on consecutive plays by blitzing linebackers Stephen Cooper and Matt Wilhelm for 19 yards in losses.

Favre and the Packers finally moved the ball on their fourth drive. A 14-yard pass to David Martin, a 28-yarder to Robert Ferguson and a 19-yard pass interference penalty put the ball on the Chargers' 22-yard line. But the drive stalled when Greg Jennings, just after catching an 8-yard pass to set up fourth-and-2, dropped a short dump-off over the middle.

"We've got a long way to go," Favre said. "We weren't very good. We have to protect better. We have to rush the football better. I don't know how many yards rushing we had, but it wasn't enough."

Favre ended up 5 of 10 passing for 66 yards. Two of the incompletions were dropped, and another was a laser-like throw intended for Donald Driver in the back of the end zone that sailed just over his outstretched body.

The Packers' first-string defense struggled at the outset but then stiffened.

On their opening drive, the Chargers marched 74 yards in just five plays for a touchdown, as Philip Rivers completed passes to four different receivers and hit Vincent Jackson for a 22-yard score.

The worst news for the Packers came two plays earlier, though, when safety Marviel Underwood went down with what appeared to be a serious right knee injury. Underwood was down for several minutes and had to be helped from the field by the medical staff.

Trailing 7-0, the Packers stopped the Chargers on their next two series, allowing just one first down on each. But the Chargers added to their lead just before halftime.

With Green Bay beginning to substitute on defense and Rivers still in the game, the Chargers drove 86 yards in 18 plays, holding the ball for 10 minutes, 44 seconds.

Running back Michael Turner capped the long possession by going around right end for a touchdown from 13 yards out to make the score 14-0 with 2:16 left in the half. The Chargers overcame two sacks and converted five third downs on the drive.

Rivers finished the first half 15 of 21 for 169 yards and one TD. Three receivers had four catches apiece, while Turner had nine carries for 43 yards, a 4.8 average.

The Chargers tacked on three points with another 18-play, clock-consuming drive in the third quarter. This one was 82 yards and took 8:27 off the clock, with Nate Kaeding kicking a 23-yard field goal to make it 17-0 with 2:23 left in the period.

The Packers finally got on the board with 12:29 left in the fourth quarter on a 23-yard field goal by Billy Cundiff.

Rodgers hit Jennings on a 47-yard bomb to open the drive. A 16-yard strike to Rod Gardner, who made a nice sliding catch on the sideline, converted a third down and gave the Packers a first-and-goal.

But a 1-yard loss on a first-down run and another loss on a second-down sack eventually forced the field-goal try.

It appeared the Packers might get back into the game after Therrian Fontenot recovered Dave Rayner's onside kick, and Rodgers moved the offense down inside the Chargers' 30-yard line. But a deep fade pass to Marc Boerigter was intercepted by Antonio Cromartie at the 2.

"We'll get better, not just as a second unit, but as a team," Rodgers said. "I don't want to say it's OK we lost, because it's not, but we made a lot of mistakes and we're going to get a lot better.

"I'm not worried at all, but there's definitely some improvement that needs to be made."