meh, his low numbers are due to his low usage % and minutes restriction. Raw numbers are useless unless you place them in context. Last time I checked, Brooklyn were like 6 or 7 points better defensively with him on the court, that's massive.
he's still one (if not THE) best per minute defender in the league. And he posted to highest rebounding percentage since 2007 this year. Not to mention he posted the highest defensive rebounding percentage of his career! this year.
So he's basically turned himself into a rebounding machine and a defensive monster who does little to nothing, except space the floor offensively.
He's going to be a key player for the Nets in the playoffs and I really do think he'll play another year, especially with 12 million on the table.