He's averaging 13.8 points and 6.5 rebounds in 20.8 minutes over the last 5 games on 68.6% shooting. Thow in 1.5 assists and 1.3 blocks for good measure.
I'd resign Tyler Zeller today and every other day of the week before I'd consider giving Jared Sullinger a contract.
When he's given consistent minutes in the right role (i.e. about 20 minutes a night as the backup center alongside guys who share the ball and can shoot), he's pretty darn good, and quite consistent as well.
But, I'd ask whether resigning Zeller is putting the cart before the horse. Sure, he is good in the role you described. But if we are going to still need to find a starting C and PF and end up playing some small ball lineups anyway, is Zeller really worth what it's going to take to keep him?
I know the salary cap is going to spike, but can we really afford to pay 10-12 million a year for a guy whose future role may be to play less than 15 mpg (a legit center should be at least 32-35 mpg, leaving potentially less than 15 mpg if we are going to play some small ball). Again, I like Zeller, but that seems like a huge overpay when we could probably get some aging vet at a reduced rate to do an adequate job at less than half the price.