SAN DIEGO - The schedule says they must play tonight.

So the Chargers will show up and face the San Francisco 49ers in the preseason finale at Qualcomm Stadium.

But there's no doubting that the veteran players can't wait to place their full focus on the Sept. 9 season-opening game against the Chicago Bears.

With the opener just 10 days away, starting players on both sides of the ball will play approximately 10 plays tonight before being pulled .

"You're not necessarily overlooking San Francisco," quarterback Philip Rivers said. "Obviously, it is a game and any time you suit up, you want to be ready to go. But it's a short week, and obviously we won't go very much in the game. It is an opportunity for a lot of young guys to get out and play.

"As we get closer and closer, we'll start really focusing on Chicago."

The game is certainly important for players on the roster bubble. The Chargers must trim 22 players by Saturday to reach the 53-player limit, so tonight's exhibition is the final chance for numerous players to make an impression.

With the starters making just a brief cameo, there will be ample playing time available for third-stringers and undrafted free agents, the latter representing a group of players primarily vying for spots on the team's eight-man practice squad.

Coach Norv Turner said some of the players who've barely gotten on the field earlier this preseason could end up getting in for between 40 and 50 plays tonight.

"I think you learn more about a player the longer he plays," Turner said. "A guy can go in for 15 plays and be nervous and not play well or he can play well and not be tested.

"Over 45 plays, I think you find more about how ready he is to handle all the things you need to see."

Though the overwhelming feeling around Chargers Park is to get through the game and start preparing for the Bears, Turner said he's excited about it.

"People minimize the fourth preseason game," Turner said. "I think it's one of the most exciting games of the preseason. It truly is. There are guys out there who aren't fighting to get ready for the season - they are doing that - but they are fighting to win a job and trying to find a way to stay on the football team."

While the starting offense is on the field, Turner will be hoping for one 10-to-12 play drive. He particularly wants the offensive line starters - tackles Marcus McNeill and Shane Olivea, guards Kris Dielman and Mike Goff, and center Nick Hardwick - to play together.

Defensively, Turner would like to see some improvement in the secondary. He was disappointed by some of the big passing plays the unit allowed last Saturday against the Arizona Cardinals.

As the game progresses, Turner plans to give third-string quarterback Charlie Whitehurst an extensive look. Whitehurst has thrown just 23 passes in the preseason as Rivers (49 passes) and second-stringer Billy Volek (44) have gotten most of the work. Volek will play for about a quarter after Rivers exits, and then the rest of the game will belong to Whitehurst.

Rivers has been particularly sharp in the preseason, completing 69.4 percent of his passes with three touchdown passes and no interceptions. He said he's itching for the regular season to begin.

"I'm ready to go," Rivers said. "You have to come out and be sharp in this last one. I think I've gotten what I needed to get out of the preseason individually.

"I think our offense has gotten, for the most part, what we needed to out of it.

"There's one more shot on Thursday, but we really now can get ready to focus in on that opener. It will be here before we know it."

- Contact staff writer Mike Sullivan at (760) 739-6645 or msullivan@nctimes.com.