Barbosa has a talent and a shortcoming, with the former being part of the reason of the latter. He is fast! But he is, naturally, too eager to exploit this advantage, so that he has not learned how to control his body position to keep options open while driving to the hoop.
Very often, he'd lower his head and shoulders 4-5 steps away from his defender trying to run by dribbling the ball. With the added momentum, rarely anybody could stay with him even then. However, the same momentum causes the problem that he is too committed to certain ways of finishing his drives. Thus, when help defense comes or occationally when his defender catches up, he would not have enough time and space to re-adjust the way Nash with his controlled body could, or Wade if you want an example with comparable athletic ability.
The same tendency of committing to certain ways to go also hurts him at defense similarly. His fouls come mostly from situations where he fail to re-adjust quick enough.
So, if he ever could learn to control his speed, he'd be much better both as a scoring PG or a defender. My advice is for him to take some Taichi classes from a Chinese master, which teaches and trains you to better focus on your own weight center and to react to any changing situation around you.
In any way, barring a spectacular playoff performance, I don't think Barbosa's market value is too high now. He is not starter material yet, anywhere in the league. His value is much lower Bell's before he became a Sun. So, I'd expect they make a 3 year deal starting at about 2.5-3 mil.