And Scal "knows how to play the game"? I mean - yes, he does. So does...everybody in the NBA. He may mentally have a good grasp of the NBA but it never translated on the court.
a) no, not everybody in the NBA knows how to play basketball. by knowing how to play i mean understanding offensive plays and defensive schemes, understanding how to play effectively in a team system, not just how to take a guy 1 on 1 like it's a pick-up game at the gym. there are a lot of fringe players and prospects in the league who don't have a great grasp of how to play the game in a team system, and that's how Scal largely sets himself apart as a end-of-the-roster guy.
b) It did translate onto the court, which is why he got playing time in the first place.
It's like other people have mentioned - during his time here Scal was often able to step into the starting lineup and not completely bring the team down. Some of our most productive lineups (albeit in limited minutes) actually involved Scal, if I recall correctly.
Most fringe players - your Semih Erdens, your Sean Mays, your Mikki Moores, your Sean Williams' etc - can't play in a system and lack basic game knowledge, which is why they don't see the floor despite their physical gifts.