Derek Fisher Says Do NOT Bench J.R. Smith, Here's Why ...

Derek Fisher is going to bat for his former player J.R. Smith -- telling TMZ Sports the Cavs should NOT quit on the shooting guard after his brain fart during Game 1 of the NBA Finals.

There's been a call from fans and NBA experts to bench Smith -- most famously from Stephen A. Smith -- who says J.R. just ain't playing good enough and needs to be benched for the rest of the series.

But Fisher ain't buyin' it ... explaining, "We're really only talking about one play."

D-Fish -- who coached Smith on the Knicks a few years back -- says J.R. played his ass off all year long and has earned his starting spot. Fish says you need to rely on the guys who got you there.

So, what about Smith's unimpressive stat line after Game 2 (5 points, 1 rebound, 2 assists in 31 minutes)??

Fisher says don't be fooled by the numbers, there are other ways for a player to have an impact.