SAN DIEGO -- With safety Marquand Manuel having yet to practice in training camp because of a calf injury, backup Marviel Underwood had been starting in his place and developing well by working extensively with the No. 1 defense.
But Underwood's progression was abruptly halted Saturday night when he left the game on the Chargers' opening possession with what appeared to be a serious injury to his right knee.
Head Coach Mike McCarthy didn't know the extent of the injury and said more would be learned by Monday. Underwood was seen on crutches after the game.
"It's a huge loss," cornerback Ahmad Carroll said. "Hopefully we'll find out what's wrong with him and he can get well and we can have him back on the field."
On a screen pass to tight end Brandon Manumaleuna, Underwood was the lone defender in the flat and was getting ready to absorb a block when he went down awkwardly and did not get up on his own.
The play went for 30 yards and helped set up the Chargers' first touchdown. But more importantly the injury is a significant setback for a Packers' defense that already was missing a starting safety in Manuel and a reserve in Atari Bigby, who fractured his hand in the Family Night scrimmage last week.
Underwood was replaced by Tyrone Culver, who played solidly and led the team with nine tackles (eight solo).
"Hopefully I did well," said Culver, a sixth-round draft choice out of Fresno State making a homecoming of sorts to southern California for his NFL debut. "I know I did what was asked of me. There were some plays I thought I could have done better. For the first game, I won't say I'm satisfied because we didn't win, but I'm in a position to keep working hard."
His teammates feel Culver's play will keep the defensive backfield from suffering despite the injuries.
"We're stacked at safety," Carroll said. "I love our safeties. They talk to you, they communicate well. I just have to do my job and make their job easier. They're doing an excellent job."
Injury update
In addition to Underwood, the Packers lost defensive tackle Kenderick Allen to a side muscle injury in the first quarter and running back Samkon Gado to a groin injury in the third quarter. Defensive tackle Ryan Pickett (finger) and tight end David Martin (hand) also sustained what appear to be minor injuries.
Defensive lineman Kenny Peterson, who dropped out of Thursday night's practice with an ankle injury, did not play.
All of the other players who sat out were not expected to play because of ongoing injuries: running back Ahman Green, receiver Leo Bookman, cornerbacks Will Blackmon, Patrick Dendy and Mike Hawkins, safeties Manuel and Bigby, linebackers Brady Poppinga and Kurt Campbell, and offensive lineman William Whitticker.
Punting, round one
Jon Ryan had the better punting night in the battle with B.J. Sander for the starting job.
On four punts, Ryan averaged 46.3 yards gross and 41.0 net. His long was a 55-yarder but his best overall punt was his third one, a 51-yarder that he angled out of bounds for no return.
Sander averaged 36.7 yards on three punts, with a net average of 33.7.
Successful challenges
McCarthy's first two replay challenges as an NFL head coach were successful, but it turned out neither victory did much good.
On the first one, Chargers quarterback Philip Rivers hit Vincent Jackson in the back right corner of the end zone for an apparent 17-yard touchdown pass with 10:44 left in the first quarter, but McCarthy challenged that Jackson did not get two feet in bounds.
Replay showed that Jackson's second foot hit the boundary line, and the pass was ruled incomplete.
But after a false start on San Diego, Jackson ran the same go route to the corner on the very next play, and Rivers found him for a 22-yard touchdown, well in bounds this time.
"The first one was probably a better throw and he still made a good catch," Rivers said. "Then we regrouped and did the same play and he made an even better catch."
In the fourth quarter, Green Bay receiver Marc Boerigter caught a slant pass from Aaron Rodgers but had the ball stripped by Antonio Cromartie, and Marlon McCree returned the fumble 78 yards for a touchdown.
Replays showed Boerigter was down before the ball came out, allowing the Packers to keep the ball. But three plays later, Cromartie intercepted Rodgers' pass at the 2-yard line to thwart the drive.
McCarthy challenged the interception as well and probably was right again. The Packers' television broadcast showed Cromartie did not have possession of the ball when he slid out of bounds. But the Chargers' TV broadcast, used by the officials, didn't have a conclusive angle to overturn the call.
Handling the ball
Rookie receiver Cory Rodgers, who has struggled to field punts consistently in practice, handled two punt returns and three kickoff returns without any bobbles or drops but was unable to break any big runbacks.
Rodgers returned the two punts for 13 and 5 yards, respectively. He averaged 16.3 yards on three kickoff returns, with a long of 19.
Coming full circle
McCarthy's first preseason game as an NFL assistant coach for the Kansas City Chiefs actually came against the Packers, on Aug. 7, 1993. McCarthy was an offensive quality control assistant for Marty Schottenheimer.
The game was played at Milwaukee County Stadium, which was not known for the most comfortable visitors' accommodations. McCarthy recalled in the Chiefs' locker room that the only place for him to hang his clothes was on a nail.
The Chiefs won the game, 29-21.
