Having checked numerous depth charts for the 49ers on numerous sites, I can't find one that lists more active cornerbacks on their roster aside from Walt Harris and Shawntae Spencer. When matching up against the Cardinals, their opponent must have three solid corners. The 49ers have two.
Since Bryant Johnson appears to have been written out of Arizona's playbook, that leaves Larry Fitzgerald and Anquan Boldin matched up against two cornerbacks that are smaller and less athletic, but possibly as physical as they are. The Cardinals, to take full advantage of this mismatch, must use motion and vary their formations in an attempt to isolate Boldin or Fitzgerald on a safety. And, when Johnson is being covered man-to-man by a lesser athlete, Arizona needs to take full advantage of it.
Matt Leinart has become far more effective as the season has progressed. He still suffers from poor decision making and the occasional lapses in the concentration that all rookies (especially quarterbacks) suffer from, but he has improved significantly in the mental aspects of the game. He is becoming far better at reading defenses, diagnosing mismatches at the line of scrimmage, identifying blitz packages and where the pressure is coming from, and finding the weak spots in the defense as it is lined up. He needs to take yet another step forward on Sunday.
With the 49ers depleted in the secondary (and their starting safeties Mark Roman and Keith Lewis are nothing to write home about), Leinart needs to successfully identify San Francisco's weaknesses and exploit them.
Former Pro Bowl defensive tackle Bryant Young is now playing end for a front four in which he is the only accomplished player. Melvin Oliver, Marques Douglas, and Ronald Fields have three sacks between them. Young alone has five. The 49ers are at the bottom of the league in sacks and the Cardinals have been on a hot streak of late, keeping Leinart upright and giving him a clean pocket to stand in. The streak of successful games in pass protection for the offensive line will continue on Sunday.
The only person who might upset the apple cart is linebacker Brandon Moore, who leads the defense with seven sacks. Leonard Davis should be able to handle Young, who, like I mentioned, is a former tackle and has had more success rushing the passer with sheer force and technique than speed. Davis may not be an elite tackle, but he is a massive man that is very rarely pushed back by a bull rush. The key will be containing Moore. For this game and this game only, it will be necessary for Edgerrin James to "shadow" Moore in passing situations, making sure that the blitzing linebacker does not get a clear shot at Leinart. Contain Moore and Young and you contain San Francisco's pass rush.
The 49ers are actually fairly good at defending the run, one of the reasons they've had success against the Seahawks this season. However, James had one of his few promising games (73 yards and a touchdown) against the 49ers in the first game of the season. Since that time, James has become more comfortable with the system, the Cardinals staff finally pieced together the right pieces for the line, and Arizona has been more effective running the ball.
With the 49ers thin in the secondary, look for them to focus more on containing Leinart and the passing game and less on stopping Edge from becoming the first 1,000 yard rusher for the Cardinals since 1998. James should find running room early and the line should be able to get a good push late in the game when Arizona is attempting to (hopefully) protect a lead.
Just bear in mind that that strategy didn't pan out perfectly in the first meeting.
Edge might be one of the few people in this game with something left to play for. He has been a disappointment for most of the season and is finally starting to come on late. He needs to sustain that success in this game and next week's game against the Chargers in order to justify his signing bonus and contract to the Bidwells. They won't release him in the offseason if he rushes for 18 yards on 42 carries and loses three fumbles in this game, but James is very into appearances and image.
If he is to dissolve the losing mentality that pervades the Cardinals organization, one of his first steps should be to perform in this game and perform well. Fitzgerald and Boldin have made it clear that they're not just playing out the string. Leinart needs to cement his starting position for next season. Every member of the offensive line is playing for their jobs.
Edge needs to take his game one level above that and show his new teammates that it's okay to be on a losing team, just as long as you don't play like a loser.
The 49ers have the league's 26th ranked defense. They are the 18th ranked run defense and the 27th ranked pass defense. They have two cornerbacks on their depth chart. Their best defense end used to be a tackle. The only linebacker on their squad that I've heard of is Manny Lawson, and that's only because he was chosen in the first round of this year's draft. The Cardinals don't need to do anything fancy. They scored 34 points on this defense before all the injuries to the secondary with Kurt Warner at quarterback. They just need to run their offense, Leinart needs to make the proper adjustments at the line of scrimmage, and everything will work.
That having been said, the 49ers are still two games ahead of the Cardinals in the NFC West. They play markedly better defense at home than on the road. Their defense does excel at forcing turnovers (led by Walt Harris' six interceptions). And, at least mathematically, they still have something to play for. If enough pieces fall into place, they could finish 8-8 and go to the playoffs. Arizona has no such chance.
What that means is this: Defense is all about emotion. It's about having the will to stay in your lane, pursue the ball carrier, and drag him to the ground. And, it's about having the confidence and the desire to make it happen. The first thing that begins to deteriorate on a team with nothing left to play for is the defense. Tackles are missed, coverages are blown, and gap discipline becomes a distant memory.
If the 49ers have given up and lost that emotion (which is unlikely, since Mike Nolan is a very intense guy), the sky is the limit for Arizona's offense. If they still have that emotion stored up in them somewhere, they're still not holding this offense to fewer than 20 points with these match-ups.
The offense's Edge will be just fine. The key will actually be if Arizona's defense has lost its edge.