You think they'd be a 55-win team with Deandre and a healthy Parsons playing at his January/February level?
I think that's a stretch. His reasoning for his original decision was wanting to be "the guy". He isn't really an offensive player. Doesn't have any reliable post moves, and if somehow he gets it going on any given night you just foul him on every play. He adds a bit of athleticism and shot blocking, sure. Probably bumps you up from 42 to 46 or 47 wins. 55 is a lot of wins though. In most cases that means you're contending for a championship. I don't think Dallas was anywhere near contending even if he came unfortunately.
I'm not that happy about Parsons wanting to potentially recruit Dwight (that is, if he stays). This fukking idiot Dwight Howard still thinks he can be a focal point of an offense in 2016. He's such a damn joke. He'll never get it. It would be better to get him than to get nothing though, because let's face it, there isn't much about playing for this current Mavs team other than Rick Carlisle that would make any star think "this is the team for me".
