I agree on the mental mistakes. A lot of it is inexperience, and not understanding that the guy sitting at the end of the bench in the NBA, was probably the star on his college team, or at least highshcool team. In the NBA, your mistakes are magnified, and he hasn't gotten that yet. Any professional athlete in any sport, is going to run into a wall now and then. That's when your tested. That's when you need mental toughness. Not saying that a sport Psychologist wouldn't help, but except in rare cases, I don't think it's necessary. When you arrive in the NBA, everything appears to be moving faster. Players seem to be quicker, and there is some truth to that perception. As a result, young players try to speed up their game, and usually with poor results. It's like taking a smooth relaxed golf swing and hitting the ball down the middle. And then, you decide you need just a couple of extra yards, and start adding a little bit more muscle to your swing. Now your swing has disappeared, and your in the tree's instead of the middle of the fairway.
When you speed everything up in the NBA, you end up in the tree's as well. When you play too fast, your brain can't keep up with what your body's doing. I agree with Funky, he needs to concentrate and work on what he does best. Larry Bird said that he would spend the offseason working on a shot from just one spot on the floor until it became automatic. Where he felt he was going to make it every time he took it. Then the next offseason, he would work on a different spot because he knew the defense was going to take away the other spot. That's the approach McLemore needs to take. Build your game one step at a time. Defensively, he needs to watch a lot of film, and stop paying more attention to the ball than the man he's guarding.