The rest of the rotation has pitched their collective asses off recently. It really sucks to have to tell one of them, "sorry, you're out" just because our own version of Wild Thing makes the most money.
He gets one start. If he can't get his act together he's gotta go. Sorry, this is a pennant race.
If it was more of a race, I'd completely agree. But I think we've got plenty of cushion and will be able to coast to the East title. I think it's a worthwhile idea to gamble with some of that margin for error and see if we can get Ubaldo pitching better, because if he does happen to put things together, he's capable of being head and shoulders better than anyone else we've got, a true ace level pitcher when he's clicking on all cylinders, even if it's unlikely he clicks like that.
I'm totally fine if you wanna stick him in the pen right now and force him to show he can keep it together for short stints first, though personally I think he's more likely to find it in the rotation than in the pen, that's just a gut feeling though.