SAN DIEGO — Russell Okung wasn't even a series into his second season when things took what has become a familiar turn for the worse.

The left tackle suffered an injury to his left ankle at some point of the first four plays of Thursday's exhibition game, forcing him out of the game.

"It was non-contact," coach Pete Carroll said. "Just to hear something kind of pop in there. X-rays were negative and all that, so we'll see what happens. He's real disappointed."

Okung's injury and a uniformly underwhelming first half were contrasted against a downright admirable second-half comeback for a 24-17 victory over the Chargers. Seattle overcame a pair of second-half deficits, scored two touchdowns in the final 4 minutes, 2 seconds and overcame a 103-yard kickoff return by the Chargers' Bryan Walters, who is from Juanita High School. Seattle's reserves made a last-minute stand at their own 5, rookie safety Jeron Johnson deflecting the final pass to force a turnover on downs. That was part of a theme as a number of Seattle rookies figured large in a victory, which was only fitting since Carroll said the young pups were the focus during Wednesday's team meeting.

"We dedicated this to the young guys, just the chance to play in the NFL," Carroll said.

Outcomes aren't everything in an exhibition game, though, and Seattle didn't do anything to alleviate concerns about the passing game with Matt Hasselbeck gone.

Tarvaris Jackson was the starting quarterback, and the Seahawks lost more yards on sacks than they gained on completions in the first quarter. Jackson completed three of the five passes he attempted, none for more than 7 yards. He was sacked twice and penalized for intentional grounding as San Diego's weapons-grade pass rush made it impossible for the offense to do much more than survive. San Diego had more passing yards on one first-quarter play — a 48-yard pass to Vincent Jackson — than the 42 yards Seattle threw for in the first half.

"There are things here and there we could have done better, obviously," Jackson said. "That's what the preseason is for."

But stats don't mean nearly as much as the potential absence of a player like Okung. He suffered an ankle injury last August, too. That was his right ankle, and a high ankle sprain forced him to miss the final two exhibition games and first three regular-season games. He hurt his left ankle on Oct. 24 against Arizona, causing him to miss three more games.

This season was going to be a fresh start for Okung, who was Seattle's first-round pick in 2010, chosen No. 6 overall out of Oklahoma State to play what is considered the most crucial position on the offensive line. Before Seattle's offense left the field, Okung was on the bench with trainers. He stood up, hopping in place to test the injury, but then was taken off the field on a cart. X-rays did not detect a fracture.

"He was setting up and pushing off it," Carroll said of the injury. "So that's encouraging, you know. It wasn't somebody fell on it or he got all twisted. But we'll find out. We don't know enough about it."

Okung was replaced by Tyler Polumbus, who played the remainder of the first half. Will Robinson finished the game at left tackle. Carroll said the team won't know more about Okung's status until further tests are done, including a magnetic-resonance image (MRI).

"We're not ruling out the fact we (could) get him back very quickly," Carroll said.

The Chargers drove 89 yards on their first possession, a drive that included Jackson's 48-yard completion from Philip Rivers over cornerback Kelly Jennings. San Diego scored a touchdown on a 9-yard pass from Rivers to running back Mike Tolbert. San Diego kicked a field goal in the second quarter and led 10-0 at halftime.

Backup Charlie Whitehurst replaced Jackson in the second quarter, completing 5 of 9 passes for 29 yards. He was markedly improved in the third quarter. He completed 9 of 11 passes in the third quarter for 86 yards and led two scoring drives.

Rookie Josh Portis entered the game at the end of the third quarter. Portis threw a touchdown pass to tight end Anthony McCoy with 4:02 left to tie the score 17-17.

The winning score was set up when undrafted rookie Pierre Allen forced a fumble from Chargers third-string quarterback Scott Tolzien, which was recovered by Seattle's seventh-round pick Pep Levingston in the Chargers' half of the field. Running back Thomas Clayton scored on a 25-yard touchdown run for the winning score.

Notes

• WR Sidney Rice did not play because of a bruised shoulder that was not characterized as serious. Wide receivers Mike Williams (toe), Kris Durham (hamstring) and Ben Obomanu (undisclosed) also did not play, leaving Golden Tate and Isaiah Stanback as Seattle's starters.

• Seattle signed DTs Ladi Ajiboye and Teryl White Wednesday, replacing DB Brett Johnson and LB Michael Johnson. Seattle needed manpower on the defensive line as Red Bryant (knee), Kentwan Balmer (stinger), Chris Clemons (ankle), Colin Cole (ankle), Ryan Sims (knee) and Dexter Davis (undisclosed) did not play.

• RB Justin Forsett did not appear in the game.

Seahawks 24, Chargers 17

SD — Tolbert 8 pass from Rivers (Kaeding kick), 4:14.

Second quarter

SD — FG Kaeding 32, 2:22.

Third quarter

Sea — Washington 1 run (Coutu kick), 7:48.

Sea — FG Coutu 28, :35.

SD — Walters 103 kickoff return (Kaeding kick), :21.

Fourth quarter

Sea — A.McCoy 6 pass from Portis (Coutu kick), 4:02.

Sea — Clayton 25 run (Coutu kick), 3:05.

A — 55,318.

INDIVIDUAL STATISTICS

Rushing — Seattle, Clayton 16-62, Washington 8-23, Whitehurst 4-13, Jackson 2-12, Reynolds 6-8, Lynch 3-8, Portis 4-7. San Diego, Todman 6-30, Tolzien 2-8, Odim 4-6, Mathews 2-5, McNeal 2-5, Tolbert 2-(minus 3).

Passing — Seattle, Whitehurst 14-20-0-115, Portis 5-9-0-69, Jackson 3-5-0-13. San Diego, Rivers 5-6-0-87, Tolzien 5-12-0-64, Volek 6-10-0-39.

Receiving — Seattle, Baldwin 4-29, Tate 3-14, Washington 3-11, Byrd 2-52, A.McCoy 2-22, Carter 2-21, Stanback 2-12, Lockette 1-16, P.Williams 1-8, Carlson 1-7, Clayton 1-5. San Diego, Todman 4-21, Jackson 2-54, Walters 2-31, Patterson 2-29, Sperry 2-19, Ajirotutu 1-15, Mathews 1-9, Tolbert 1-8, Rogers 1-4.

Missed FG — None.

Danny O'Neil: 206-464-2364 or doneil@seattletimes.com