Justin Bieber -- Kicks It with Neymar ... Impressive Juggling Session (VIDEO)

More legitimately impressive displays of athleticism from Justin Bieber ... with special guest, Neymar.

The Brazilian soccer superstar touched down in L.A. Thursday -- and beelined it to Bieber's pad ... where the two hung out for a bit ... before busting out the soccer ball for a juggling session.

Of course, Neymar's skills are insane (as to be expected) ... but Bieber wasn't too bad either.

In fact, he's pretty good.