And it's not about effort. All players expend effort. If Bargnani tried harder he'd likely just play even worse defense. He has no aptitude at all for defense. If a person who is not a brain surgeon tried really hard to perform brain surgery, he'd cause more problems than if he left well enough alone. If Bargnani expended more effort on defense, he'd overcommit to the wrong spot, leave his man too quickly or something like that. Great defenders effortlessly wreck offensive game plans. Just by standing in a certain place and holding their ground.
The only thing that will fix this team's defensive woes is new players.