Devin Booker is clapping back at the haters after the Suns lost to an Australian basketball team on Sunday ... by posting LeBron James' infamous reaction to losing the 2011 NBA Finals.
Booker and the Suns -- who played all five starters -- lost to the Adelaide 36ers, 134-124, in their first preseason game ... the first time an NBA team lost to a National Basketball League team.
After the L, Book posted a screenshot of LeBron's viral speech following the Heat's Finals loss .