I think it'll take about until the playoffs to really get things together. It took Sam a long time to understand the offensive sets last year; Marbury could similarly struggle.
I agree it could take that long. However, a big difference with Marbury and Sam are their respective games. Once it was clear to Doc that Sam was not going to be able to run much, he looked for him to score, mostly by posting. Many here hated him for that, even though it was essentially his coach asking him to do it with who he was on the floor with at the time, but it was trick or treat with Sam's fadeaway.
With Marbury, he is able to beat his man off the dribble, which may result in him trying to score, but will often result in an opportunity created for a teammate. Therefore, even if he struggles to learn the sets, his game is more conducive to making a more immediate contribution, especially in the open floor, than was the increasingly calcified Cassell's game which was so one dimensional.