This is completely speculative, but if you watched Joba pitch on Tuesday night, I'm sure you noticed that he was using his curve instead of his slider. The obvious question is why.
There are a couple of explanations, some mundane like maybe he just had a better feel for the curve in the pen than the slider. One possible reason is elbow tenderness. The slider is much harder on the arm than the curve, especially the type of slider he throws. One possible explanation is very interesting. We may be witnessing the beginning of the transition of Joba into the starting rotation that we've all been anticipating since the Winter.
If the timetable speculated upon over the Winter and Spring is to be believed, Joba only has about another three weeks left working out of the bullpen, maybe the team told him it's time to start refining his third and fourth pitches in preparation for the move. It's possible, and I guess only time will tell. If Joba goes back out there and breaks off nothing but heat and sliders the next time he's called upon, I'm probably wrong, but if we start seeing a four-pitch reliever in the 8th, I think I may be on to something.
I'm not really sure how I'd feel about this, if it proves to be true. Honestly, I think he's more dominant with his two best pitches when he only has to face a handful of hitters once. Mixing in all of his pitches in that role is asking for trouble.
Anyway, food for thought heading into the day game today, and something to keep an eye on.