Robinson was the Big Ten Offensive Player of the Year as a Penn State quarterback. Because he was not considered a great passer, NFL teams did not envision him as a quarterback when it was time to enter the NFL. Now, he is taking some snaps in the shotgun formation.

Robinson has been used in that formation for the past two games. He has handed off to Gore on all three of the snaps he's taken. However, with Robinson's versatility, he is undoubtedly capable of performing other tasks, too. Recently, receiver Arnaz Battle, also a former college quarterback, ran the option and delivered a pitch to Gore.

Also, the 49ers signed center Eric Heitmann to a contract extension through the 2011 season.

PLAYER NOTES

--WR Isaac Bruce has a team-leading 350 yards receiving this season, but 153 of them came in a Week 2 victory over the Seahawks. Bruce has been held under 60 yards receiving in each of the 49ers' other six games.

--DE Kentwan Balmer is expected to see extensive playing time this week with Ray McDonald out with a knee injury. Balmer, the team's first-round draft pick, has 11 tackles in seven games.

--QB J.T. O'Sullivan is the 49ers' second-leading rusher with 146 yards on 29 carries. His long run of the season, 18 yards, came last week in the 49ers' loss to the Giants.

--RB DeShaun Foster has gotten little playing time as Frank Gore's backup. In the past three games, Foster has three carries for 4 yards and has not caught a pass.

--LB Patrick Willis leads the 49ers with 85 tackles, according to the coaches' review of the game film. He has a team-leading nine passes broken up. In the first meeting against the Seahawks this season, Willis returned an interception 86 yards for a touchdown.

GAME PLAN: Typically through the years, 49ers coach Mike Nolan has preferred to play five defensive backs on all downs against the Seahawks. Nolan believed that Mike Holmgren's passing game deserved additional attention, as the Seahawks have not been an efficient running team for a while. That strategy will probably go out the window this time, as Mike Singletary takes over as head coach and the Seahawks with Seneca Wallace at quarterback do not have a formidable passing game. The Seahawks figure to be without injured QB Matt Hasselbeck. Also, the 49ers want to get more playing time for Manny Lawson, who is the first linebacker to come off the field when the 49ers go with extra defensive backs. When the 49ers played the Seahawks earlier this season, Lawson did not play one snap from scrimmage. Offensively, quarterback J.T. O'Sullivan threw for 321 yards in the previous meeting. He has fallen on difficult times with 12 turnovers in the past three games. O'Sullivan has to take better care of the football, which includes keeping him out of third-and-long situations. The 49ers will try to utilize running back Frank Gore, as always, but they might also try to hit the Seahawks in the passing game on first downs. Offensive coordinator Mike Martz could call more high-percentage passes on first and second downs to keep the 49ers out of those third-and-long situations.

MATCHUPS TO WATCH: 49ers RB Frank Gore vs. Seahawks MLB Lofa Tatupu - Gore was held to just 11 yards on 11 carries against the Giants. Tatupu is the Seahawks' leading tackler and a key against Gore breaking the long run.

49ers CBs Nate Clements and Walt Harris vs. Seahawks WRs: Clements and Harris have fared better this season against established veteran wideouts. They'll face a Seahawks receiving corps that is beginning to get healthy.

49ers RT Barry Sims vs. Seahawks DE Patrick Kerney: Sims has played a couple good games in a row after a rough beginning. Kerney led the Seahawks with 14.5 sacks last season.

49ers LT Joe Staley vs. Seahawks OLB Julian Peterson: Staley was beaten a couple times in the opener on speed moves. Peterson will use his quickness to rush the passer from the outside.

49ers QB J.T. O'Sullivan vs. Seahawks FS Brian Russell: O'Sullivan committed 12 turnovers the past four games. Russell will be trying to read the quarterback and react on the ball.

49ers LB Manny Lawson vs. Seahawks TE John Carlson: Lawson figures to get a lot more playing time this week against the Seahawks. Carlson tore up the 49ers' five-DB defense in this year's earlier meeting.

INJURY IMPACT:

--S Michael Lewis returned to limited practice Thursday after missing Wednesday with a mildly sprained knee. Lewis ranks third on the 49ers with 47 tackles, according to the coaches' review of the game film. Lewis is second on the team with five passes defensed.

--S Mark Roman returned to limited practice after sitting out a day's work with a groin strain. Roman has started every game at free safety for the 49ers this season. He has recorded just one interception in 39 games with the 49ers.

--WR Josh Morgan returned to limited practice with a groin strain. Morgan was the 49ers' No. 1 split end the past two weeks with Bryant Johnson nursing injuries. Offensive coordinator Mike Martz said he has not decided which player will start when both are healthy.

--DE Ray McDonald has been ruled out of Sunday's game with a knee sprain. McDonald has started all seven games. He has one sack and 17 quarterback pressures this season.

--DE Kentwan Balmer, the 49ers' first-round draft pick, is expected to make his first NFL start on Sunday with Ray McDonald out of action with a knee injury. Balmer has not had much of an impact through the first seven games with 11 tackles.