A quick glance at your team shows that you have a weakness in your INF. Especially 2B, 3B, and SS.
You are going to have to bank on the fact that Hall, Mackowiak, and Beltre are enough to pull you through. That's a prospect that would have me sweating.
Beltre has upside and could get real hot. Mackowiak though. Eep.... Hall may have trouble keeping it up as well. I'd probably try to add a 2B or SS and try my luck with Beltre. If you add a 2B or SS then slide Hall over to the other position and use Mack as your backup.
Your SP also is a little on the weak side for a championship run. You have the tools you just may falter a bit down the stretch. Burnett is struggling lately. Can Garland keep it up? That remains to be seen. Watch his ratios steadily rise from here on out. Zito remains a question mark as he has been all season but I like him from this point on. You're also going to need to find another reliever. I'm not sure where but you'll have to grab one somewhere. Browse the WW look for guys like Duchscherer in case Street goes down for a long period of time.
I'd drop Mike Gonzalez and Kolb to find better replacements in your RP as well.