My main problem with Gasol is that while he's a good offensive player, he's not a dominating offensive player. That would be perfectly fine if only he wasn't atrocious on defense. If he's standing under the rim, he can get you some blocks, but if he has to move out just 5 feet, he's terrible. In today's NBA where PG's and wings are ultra athletic all over the place, he gets lit up. Besides that, he's soft as wet tissue. He gets bullied for rebounds, instead of dunking the ball, he'll try to lay it up and miss, and when matched up against a player of equal length and good strength, he's ineffective in the post and is turned into a spot up jump shooter. Combine that with the fact he's going to opt out next year and the Bulls aren't a true contending team (IMO), it's a no brainer why people want him traded.
I realize that's not the OP's premise, but this is a thread about Gasol afterall and this board is here for conversation. Like I've said already, Gasol isn't terrible. He isn't our only problem on the team. But he still should be traded because of everything else I and others have said.
