Antonio Brown's new teammate is already going to bat for the star wide receiver ... 'cause Tyrell Williams tells TMZ Sports AB is 100 percent NOT a locker room cancer!!
"He's awesome," the stud receiver says ... "We love him. We love him. It's been fun."
Of course, there are a few dudes in Pittsburgh who'd disagree ... Brown left the Steelers on bad terms a few months ago -- and everyone from JuJu Smith-Schuster to ex-teammate Ryan Clark blasted the guy.
But, it's so far, so good in Oakland ... so says Tyrell (who just signed with the Raiders this offseason himself), 'cause the WR tells us he's actually learning some tricks from Brown.
We also asked Williams if he thinks Derek Carr and Brown can be a better duo than Big Ben and AB were ... and Tyrell said, "Sky is the limit. You never know what's going to happen."
BTW, we also spoke with Tyrell about the Raiders' future move to Vegas ... and he says he's got no worries about the future trek to Nevada!