While I do agree that they are generally overworked, especially the two Japanese pitchers, Tazawa had last been used on Wednesday. Dempster, Lackey, Lester, and Buchholz had done a good job recently of eating innings. They have to keep it up and hope that some relievers come back strong so it's not just Uehara/Tazawa that are reliable.
And if we can find a 5th starter that can get some outs without walking the ballpark, then our bullpen should be in good shape going forward, especially with Morales coming back.