Lyle Sendlein is the only healthy center on the roster. Al Johnson, the regular starter, will miss the first game or two while recovering from knee surgery. The Cardinals didn't keep another center on the roster, so tackle Reggie Wells and guard Elton Brown are getting some work there this week in the event of emergency.

Bryan Robinson will start at nose tackle, even though he's a better defensive end. Backup Alan Branch is struggling with a sprained ankle, and Gabe Watson is just easing into practice after missing camp while recovering from a fractured kneecap.

Defensive end Kenny Iwebema, a rookie, is working at nose tackle.

Coaches are gambling a bit by not going short in other areas in order to keep a backup center and nose tackle for only a week or two. If the Cardinals can make it through a week or two unscathed, they should be in good shape.

PLAYER NOTES

--WR Larry Fitzgerald enjoyed one of his best training camps and appears primed for a big season. Fitzgerald has worked harder than ever, even though he received a four-year, $40 million deal in the off-season.

--RB Edgerrin James likely will have some of his workload reduced this year due to the emergence of rookie Tim Hightower. James carried 324 times last year, while his backups had just 42 carries. Look for Hightower to get more than 100 if he doesn't fumble too much.

--TE Ben Patrick returned to practice this week after missing some time with a sprained ankle. Patrick is the team's No. 2 tight end behind Leonard Pope, but he was pressing Pope at the time of the injury.

--OT Brandon Keith, a seventh-round pick, impressed coaches in camp. He's at right tackle now and has worked some at guard. Coaches think he can eventually play the left side.

--TE Leonard Pope has looked better in recent weeks after struggling early in training camp. Pope suffered a dislocated ankle and fractured leg late last season and didn't seem up to speed when camp started. He's been running better of late and has made some nice catches.

--WR Steve Breaston will be the team's No. 3 receiver, but he's being pressed by Jerheme Urban. Neither has filled that role on a consistent basis. Breaston is in his second year, and Urban has struggled through some injuries and has dropped some passes in traffic.

--QB Brian St. Pierre is No. 3 on the depth chart, but coaches won't panic if he has to play. St. Pierre, who came from the Steelers, knows the offense well and looked great in the preseason.

MATCHUPS TO WATCH: Cardinals ILB Karlos Dansby vs. 49ers RB Frank Gore - The 49ers likely will try to throw the ball some to Gore, one of the game's great scoring threats. Dansby has great range and is a playmaker, so this will be a strength vs. strength matchup.

Cardinals SS Adrian Wilson vs. 49ers QB J.T. O'Sullivan: O'Sullivan must know where Wilson is at all times. That's harder than it sounds because Wilson will line up at safety, inside linebacker and will blitz up the middle and off the edge.

Cardinals WR Larry Fitzgerald vs. 49ers CB Nate Clements: Clements usually guards the most dangerous receiver, and that likely is Fitzgerald. Fitzgerald will try to use his size and strength and can be dangerous if he's covered by one man, even if that man is pretty good.

INJURY IMPACT:

--NT Alan Branch didn't practice on Thursday, so it looks like starter Bryan Robinson will be holding down that spot alone on Sunday. Branch (ankle) needs to practice on Friday in order to play Sunday.

--DE Kenny Iwebema is practicing at nose tackle in case Branch can't play.

--NT Gabe Watson (knee) is expected to begin practicing soon. He suffered a fractured kneecap in the off-season and hasn't been cleared to practice.

--C Al Johnson is at least a week, and probably more like two, away from returning to the lineup. Johnson underwent knee surgery in late July. Lyle Sendlein has taken his place and is a solid player.