Jim Palmer and Earl Weaver have both discussed Mussina's lack of desire in holding fast / going into the late innings. Ray Miller often referred to him sarcastically as "Miss-ina" for this reason.
Sorry I can't provide a link. He looks done to me as well, though, I have ALWAYS said we need a veteran pitcher - a hall of fame pitcher to set the tone for the staff. I so very much wish we could've traded for Greg Maddux way back.