Oakland Raiders starters will play the first half of Saturday’s preseason game against San Francisco at Candlestick Park, but coach Tom Cable said you can expect to see Jeff Garcia, the team’s top back-up quarterback, getting action somewhere in the second quarter.

Garcia will be facing his former team in the Raiders’ second game of the exhibition season, which kicks off at 5:15 p.m.

The Raiders and 49ers should know something about each other, as they took part in joint practices at Redwood Middle School Tuesday and Wednesday.

Oakland’s quarterback rotation will have Bruce Gradkowski playing in the third quarter and Charlie Frye in the fourth quarter.

“I think everything we’re doing is important in terms of evaluation,” Cable said Thursday. “We had two good days of work with (the 49ers). It’s another chance to play a game and I want to work on some things we didn’t do in the first game, and then improve.”

It marks the halfway point of the preseason for Oakland, which will play New Orleans on Aug. 29 and then Seattle on Sept. 3. The regular season starts Sept. 14, with Oakland taking on San Diego.

More than anything, Cable is looking for improvement from Week 1 of the preseason, a 31-10 win over Dallas. The starters, he said, will get more playing time Saturday.

“We’re going to really have the same idea we had going into Dallas,” said Cable. “We want to just get guys evaluated.”

Darrius Heyward-Bey, Oakland’s top pick in this year’s NFL Draft, will start at wide receiver against the 49ers.

Yesterday marked Oakland’s 30th practice of camp, and several players, mostly veterans, didn’t take part in the drills. It was an afternoon session.

“We gave a bunch of guys rest today,” said Cable. “Other than that, really good work I think by both sides.

“It got a little lethargic there at the end, but we’re tired and we’re deep into camp now.”

Raiders Notebook

• KTVU-Channel 2 and KPIX-Channel 5 will both carry Saturday’s preseason game. It marks the 37th time the Raiders and 49ers have faced each other in exhibition action. 

• Raiders owner Al Davis was on hand for Thursday’s practice, watching from a golf cart.

• Yesterday was a padded practice, but there was light contact, even during the 11 on 11, offense vs. defense period.

• The Raiders have a walk-through today at 10:15 a.m. The players have Sunday off.

• Next week’s schedule hasn’t been announced, but the Raiders are expected to wrap up camp, their 14th year in Napa, on Aug. 27.

• The first roster cutdown — in which teams have to trim their rosters to a maximum of 75 players — is Sept. 1.

• The second roster cutdown — with teams reducing their squads to a maximum of 53 players — is Sept. 5.