Manager might also have been trying to show confidence in Sosa. He is a better hitter than he has shown this year. I don't think Thomson likes to bury guys on the bench as much as Girardi did. They want Sosa to get 2-3 starts a week and pinch hit against some LHP. If Stubbs had not hit the previous HR against the guy this move would have not been questioned. Sosa against LHP is probably a better hitter long term than Stubbs is. He just has not been this season for whatever reason (much of it SSS for both Stubbs and Sosa).