TLR (especially in conjunction with Dave Duncan) is known for manipulating his starting pitching rotation so that his pitching matchups are better weeks down the road. I don't know the details but I would guess TLR started Lohse today because he thinks this will give him better matchups when the Cards play the Reds.
It's a smart move by TLR (much as I can't stand him I have to admit this). If you're a Cards fan, you'd trade off losing today against the Cubs for a win against the Reds in a few weeks. The Reds games are worth twice as much since they're competing to win the division.