I think even at an NBA level it takes a special person to play his hardest knowing that he is never going to shine offensively even when able to do so. I'm not talking about a defensive specialist either.
I think Westbrook does just a little too much on offense for the Thunder. It's natural for a person to play that much harder when they are directly involved in the scheme and especially on offense to a degree. There's that extra gear that kicks in when you are doing well in a game and not defaulting everything to that one guy.
Plus you can't tell me a top notch offensive player is drooling to go play with Westbrook right now.