This is just my opinion, so take it for what its worth:
I think our run defense needs to excel more than any other area. Here are the reasons I think so:
1.) One-dimensional - Cal plays in the PAC 10, which is notorious for being a passing conference. However, Cal is not your prototypical PAC 10 team, as they have 2 very good runners and they won't hesitate to run it down our throats. If we can keep Cal's rushing attack in check (you can decide what that encompasses), then they will need Longshore or Ayoob to beat us, which I don't think can happen. Not with our secondary, not with their QBs.
2.) Clock Possession - The more Cal successfully runs the ball, the more time our defense will be on the field. The major issue for UT this season on both sides of the ball is depth. The longer our D is out there, the more the inexperienced players will play. If we stop the Cal rushing attack, we will control the clock, keep our players fresh, and in turn, our BETTER 1st team will beat their 1st team.
3.) Confidence - If and when our run D shows that Cal isn't going to be able to pound it on us, they will probably panic a little. Cal knows they have one of the better rushing attacks in the nation, but when stopped, they don't have a ton to rely on. Last season, they only rushed for 79 yards or so against Oregon State, and lost by a FG. Rush for 79 yards about Tennessee, and they'll lose by 17+. Stop the rush, kill their confidence.
So, stopping the run will make Cal one-dimensional, it will keep our 1st team players fresh, and kill Cal's confidence.