Haters can save their breath when it comes to JJ Redick ... 'cause his former teammate, Matt Barnes, tells TMZ Sports the Lakers coach simply "doesn't give a s***" about any outside noise.
Barnes played with Redick on the L.A. Clippers from 2013 to 2015 ... and if there's one takeaway he got from their time together, it's that the dude stays focused on what matters -- and definitely knows his stuff.
Now that Redick has landed his first head coaching gig (with the Purple and Gold, no less), all eyes are on him ... and naturally, that puts his performance under the microscope.
But Barnes says none of that matters to Redick ... 'cause ultimately, he's a seasoned vet when it comes to blocking out the negativity.
"He doesn't give a s*** about criticism," Barnes said. "He played in the NBA long enough and been a star for long enough to let it go in one ear and out the other."
Barnes continued to defend the 40-year-old coach ... saying Redick is doing a good job of giving the Lakers an identity and empowering the players.
He also believes Redick will put in the work ... and despite it being early in the season, he expects the Lakers to have a big year.
"This team has a chance to do special things," Barnes said, "He's done a great job so far. I'm looking forward to the rest of the season."