It doesn't concern me. It's similar to last season.
Our best prospect (Liriano/Garza) is the odd man out of the rotation for Silva and some other older player we are trying to let in (Lohse/Ponson).
Of course, sometime early into the season, Silva and the older, tenured player will be demoted to the bullpen or minors, making room for the prospect. They will then go on to dominate with Johan. Of course, this time Garza won't be injured.
In all seriousness, I'm not in love with the rotation. It's not sexy (especially Ponson, Silva, and Bonser in those pants!) but if we can get decent outings and still be in the game when our pen gets in the game, we'll be fine until Garza and Slowey and Perkins are ready.
Besides, we got Johan.