Can't grow new brain
I don't think it is an IQ thing. You can see him anticapate plenty of plays but he gives no real effort. Young lacks aggression and focus, he can't keep waiting for things it's the NBA and he has to be "locked in". Too many years coasting on superior talent vs the competition as made him weak.
Sooo...Adderall, anyone (sarcasm)

? All kidding aside, I think it'd be better for him to work with Pierce, instead, just because Paul is an old school guy, or even Michael Redd because things are different for lefties. Plus, Pierce can give Ainge his assessment of Young and tell us whether or not he 'passes his test.' That way, we keep things more in-house, and James could spend the summer working out and playing pickup games with Pierce and KG, not to mention Paul George and/or Kobe (there was an article that said Pierce, KG, and George played pickup games in 2011, iirc, and that's when Demarre Carroll really put himself on the map, as Paul and Kevin then lobbied Danny heavily to get the now-Raptor as a replacement for Tony Allen.). Man, what a job, lol

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