Andrew Church -- a 2nd-round pick by the Mets in 2013 -- just exploded on his former squad after they officially released him this week ... taking aim at Tebow's signing in the rant.

“The Mets made a mockery of our team by putting a celebrity on it to sell more tickets,’’ Church wrote. "I saw players lose their jobs because of it."

He added, "We weren’t playing to win, we were playing to make everyone else money. Not the players. We never saw a cut. Well, allegedly one player did."

25-year-old Church never directly named Tebow in the post ... but it's pretty clear he's talking about the former Heisman Trophy winner -- whom Church was minor league teammates with in 2017.

Of course, Tim officially signed a minor league deal with the Mets in '16 ... and at the time, NY general manager Sandy Alderson said the move was strictly made because of Tim's baseball potential.

But, Alderson reportedly later admitted he inked Tim to a deal "partly because of his celebrity, partly because this is an entertainment business."

32-year-old Tebow has shown some flashes of being a potential big leaguer in his minor-league career ... but it's largely been a disappointment for the ex-NFL player -- he's batted .231 or worse in all but one of his seasons.

Church, meanwhile, also ripped the Mets for an injury he suffered in his career ... claiming they forced him to pitch when his body wasn't ready.

Church says he decided to go forward with his rant Thursday because "now that it’s officially over with them I’d like to say some things."