A top of the rotation starter would be a #1 starter, ie an ace. Also, Haren is coming off a back injury and a loss of velocity. He could certainly regain that status, but he's far from certain. Now, I think he is a great idea for you guys, but counting on him to lead your rotation is probably not wise if you plan on winning the AL East next yr. If your plan is to build talent and place hold until 2014, then he is a wise decision, especially since you could get a draft pick for him if he signs a 1 yr deal.
I honestly think he'd be a great idea for NY. 1 yr deal, lots of incentives and if he returns to glory he is solid. If he doesnt, then we have the depth to eat the loss. I wouldnt count on him though