In my opinion, experience weighs quite heavily, and in the GE it should be something like Game Shape. I mean, the more experienced a player is, the better he plays. Even if you have terrible player, with high experience, he should play quite well.
In terms of affecting performance i can tell you this much. In close games, with the game (and shot) clock winding down, your most experienced player on the court will almost always get the ball for the final shot, and he will find a very high percentage shot and take it. For example i have a 2k salary scrub, who I used to play in cup games last season versus bot teams, and he would always have a nice impact(double-digit scoring, few turnovers, and always took the final shots). The more experienced a player is, the more he understands how to use his skills better