Comparing Landry Fields to Shane Battier is very accurate IMO...but Battier at his peak is probably a better wing defender than Landy Fields will ever be, if only because he's got a lower ceiling athletically.
Quick synopsis on Fields: A bulky 6'7, was a power forward @ stanford where he was the primary scorer. Quicker than the PF's that tried to guard him but stronger than the SF's, he was the best player Stanford had out there last year. People though questioned where he fit in as a NBA prospect because he didn't look like he was built athletically for the wing, and he didnt have the bulk for the 4.
Wowed people during the summer league and D'Antoni loved him right away because he never forces anything. He lets the game come to him, and that's one of his biggest assets. He isn't on LeBron James's level or anything as a passer, but he makes good smart passes (lots of basketball nerds have been recently raving about his entry passes to Amar'e Stoudemire..Kelly Dwyer even went so far as to say he'd never seen anyone at any level do it as well). He's not on Ray Allen's level as a shooter or anything, but he's good enough to hit open shots when he has them, or put the ball on the floor and draw a foul when he needs to. He's not on Tony Allen or Aaron Afflalo's level as a man defender on the perimeter (case in point, Ray Allen lit him up...Fields couldn't get through those screens to save his life), but he plays good team defense, he's long, and he doesn't give up on plays.
He's never going to be an All-Star..but as far as a guy you want to have around, I'd compare him a lot of Shane Battier. A humble kid who wants to play his heart out and is content to let the game come to him. Not the lockerroom leader Battier is, but even that might come eventually.