Teheran and Miller are your controllable upside guys. Both have pitched very well and are young ... always risk coming into the division, and as always, price matters.
James Shields is possible too. Now, while I did not like him as a premium FA signing - he does have AL East experience, and is a good bet to at least provide some solid bulk. I would not give up much, but there is a solid case for him.
Some guys I think Dombrowski will be watching as the season unfolds:
Anibal Sanchez - who has been awful so far, but has been good before and might be a buy low opportunity.
Personally, the interesting guy to me if you want to take a plunge, use some prospect inventory and really go for it ... is Justin Verlander. Yes, he is on the other side of the mountain - but his fundamentals have not changed all that much - and if the Tigers slip further off the pace, it doesn't hurt to ask.