Kevin Durant Joins Shaq, JaVale McGee Beef ... Shaq Tells K.D. To Stay In His Lane

Kevin Durant dove headfirst into the Shaquille O'Neal vs. JaVale McGee beef ... and Shaq ain't havin' it.

The Warriors superstar backed JaVale (his teammate) and took shots at Shaq ... including telling reporters the 4-time NBA champ was acting "childish" and unnecessarily ruining McGee's career.

Now the Big Aristotle has clapped back at K.D. ... saying "mind yo business this ain't for you."

"I understand u sticking up for your teammate that's cool but your boy @JaValeMcGee34 is still a bum, he started it I'm a finish it."

Shaq was double-teamed a lot during his NBA career ... didn't stop him then, won't stop him now.