I disagree that Kanter is a subpar defender he was great for us during our playoff run two seasons ago, not a great shot blocker but still a strong, aggressive rim protector, who can get out and defend the pick and roll. Gary is almost certainly coming off the bench and is a fantastic defender. Hoodie, Jones or both are coming off the bench and they're both great defenders (I know Hood is coming off his injury but the way he played using his length, strength, footwork and angles, his D shouldn't really be effected). Zach will probably be back within a month and he may foul a lot but outside of that he's a really good defender.
Simons probably won't crack the rotation, I actually think that Nas and Wenyen will get more chances than him and they're both good defenders that have potential to be great. Our worst defender is probably Simons, the guy is just lost out there but our second worst defender is CJ and he starts and our third worst defender is Melo and I have no idea what his role is going to be it could be as a starter, a key backup or a guy who just gets spot minutes when we need some scoring.