Good news Dodger fans ... the team's epic collapse ain't NOTHING to fret about -- so says ex-GM Ned Colletti, who assured TMZ Sports that everything was A-OK when we got him out in Beverly Hills. 

Okay, so here's the thing -- the Dodgers are in the middle of an EPIC slump, losing 16 out of their last 19, and seeing a 20 game NL West lead shrink down to 9. 

They've won their last 2 though, and we guess that's enough for Colletti to pop some champagne ... 'cause when we found him in the 90210 he told us, and all the fans, to just CHILL.

Whatever you say, Ned.