Nearly seven months ago, the Packers 15-win regular season came to a crashing end in the divisional round of the playoffs, largely due to four costly turnovers against the Giants. Although the offseason focus concentrated on upgrading the moribund defense, a noble mission given Green Bay’s league-worst finish, concerns about ball security and possession miscues were mostly overlooked.

That proved to be shortsighted, as the Packers committed four turnovers Thursday night in a 21-13 loss at San Diego, the nationally televised preseason opener for both teams.

Coach Mike McCarthy, who preaches ball security as a tenet of his offensive philosophy, said after the game, “Obviously the way we handled the football, the ball was on the ground way too much. We spend extra time on handling the football, and I think when you do emphasize particular fundamentals in practice, it needs to show up in games, and that was not the case. So we have work to do there.”

Granted, it was the first preseason game and the Packers displayed little evidence of a gameplan. But it was especially concerning to see two of the turnovers come from the No. 1 offense and another on special teams from a player thought to be in the mix for a 53-man roster spot.

On Green Bay’s first offensive possession, RB James Starks started running before securing a handoff from QB Aaron Rodgers and dropped the ball. The fumble was officially charged to Rodgers but the mistake was clearly on Starks. Making that gaffe more glaring was that, six plays earlier, Starks had dropped an easy pass that would’ve moved the Packers out from inside their 5-yard line.

Then, second-year WR Diondre Borel, who’s trying to convince the Packers to add yet another receiver to the roster, hurt his chances by erring on special teams. He fumbled his team’s first kickoff return, giving the ball away at Green Bay’s 17-yard line.

The next offensive drive was a three-and-out punt. Then, on Rodgers’ third and final series, he was pressured and hit by Chargers rookie LB Marvin Ingram, and flung a fluttering interception Antoine Cason. That was the end of the night for most of the starting offense, but it wasn’t the end of the turnover carousel.

In the fourth quarter, on the game’s penultimate play, Marc Tyler lost a fumble after a 6-yard reception that sealed the Packers’ fate. Returner Shaky Smithson also fumbled, but he recovered his blunder.

“Stuff happens,” said Rodgers, who was 2 of 8 for 16 yards for a 0.0 passer rating. “You don’t play as well as you want to, but it’s preseason. We’re missing some guys, screwed some plays up, turned the ball over. It happens. We’ll watch the film, review and get better.

“Whether you play real well or you struggle, it’s preseason. You’ve got to be working on things. We’ll be fine. We’ll just watch the film, get a nice tongue lashing, come back on Saturday and get ready for next week.”

On the other hand: The Packers defense forced three turnovers. Last year, they led the league in INTs (31) and takeaways were often the only way the defense could stop opposing offenses. CB Tramon Williams had a beautiful INT in the first quarter, getting in optimal position and impressively snagging a poor Phillip Rivers throw. 

Later, S Anthony Levine, an undrafted free agent who the Packers loved before he suffered a concussion in last year’s camp, went up for a pretty pick-off of Jarrett Lee. And in a breaking-news story, LB A.J. Hawk, who made all of zero turnover plays in 2011, recovered a fumbled Chargers handoff in the first quarter.

Two defensive starters injured: ILB Desmond Bishop grimaced as he was helped off the field with a visibly painful leg injury on the defense’s second series. He’d been down on the field several minutes after a Chargers player landed directly on his extended right leg as he was trying to make a tackle. Afterward, McCarthy called it a “knee sprain,” which in McCarthyspeak can mean almost anything in terms of severity, and said there was knee and hamstring damage. “Desmond’s injury didn’t look very good,” the coach said. Second-year ILB D.J. Smith replaced Bishop.

In the third quarter, second-year CB Davon House was covering a punt – why the frontrunner for the No. 2 CB job was playing special teams in the third quarter is anyone’s guess – when he hurt his shoulder. House, who’d played an excellent game, tweeted Friday that he was to have the injury examined Friday afternoon. More information on both players will be provided after practice on Saturday. The Packers went into the game at San Diego with 18 players not in uniform with varying degrees of ache and injury.

Potent punting again: P Tim Masthay is the real deal. He’s had a sterling training camp, an excellent intrasquad scrimmage last week, and a very good preseason opener Thursday against the Chargers. Having signed a contract extension in July that keeps him in Green Bay through 2016, Masthay is showing he’s deserving of the deal. He punted eight times for a 49.5-yard average, with a 62-yarder and a couple of well-placed 50-somethings. In Green Bay, with its awful recently punting history, simply getting the kick off is practically a success; Masthay is redefining the position for the Packers.

Another Jones drop: WR James Jones, who’s been plagued by and maligned for his tendency to drop big passes in important situations, did nothing to quiet his critics Thursday. In the first quarter, Rodgers lofted a perfect pass to Jones, who was 35 yards deep on the left side of the end zone. The throw hit Jones on the hands, bounced around and eventually fell to the ground. The play would have been negated anyway for an offensive holding penalty, but it was a damning drop for Jones, who signed a contract extension last year but may be playing for his job.