David Ortiz just went OFF on Mike Fiers for blowing the top off the Astros' cheating scandal ... with Big Papi straight-up calling the ex-Houston pitcher a "snitch."
"I'm mad at this guy, the pitcher that came out talking about it, and let me tell you why," Oritz said at Red Sox camp Thursday. "Oh, after you make your money, after you get your ring, you decide to talk about it?"
"Why didn't you talk about it during the season when it was going on? Why didn't you say, 'I don't want to be no part of [this]?