Marshall cannot and will not be an NBA player unless he develops a shot. People will play 5 feet off of him rendering him ineffective. I like the kid and want him to succeed, but unless he develops a shot he won't.
His shot isn't that bad. He shot 40% last year from three. Give him 5 feet and I think he can do that again. True he isn't a great shooter and won't be draining any J's in people grills anytime soon, but he can hit the open jumper at a decent rate.