I like Kessler but I still don't buy him as a long term NBA starter. At least not with his current offensive repertoire.
It's a pick and roll league, and Kessler is just so incredibly limited there. All he can do is roll slowly through the lane, bringing his defender with him and clogging up the middle. I'm not expecting him to suddenly turn into some pick and pop beast – a much more pressing need is becoming a better free throw shooter – but he needs to show he can make at least some jumpers or floaters from the FT line area off short rolls, to keep defenses honest. Kessler is way too easy to neutralize with drop coverage right now. I wouldn't use him as a PnR screener much before he adds to his game.
I don't want to sound too critical though. He's just a rookie, and to say the kid has exceeded my expectations on the defensive end is the understatement of the year. He seems to be a quick learner and doesn't back down from anyone.