EXCLUSIVE

Bautista's very first professional MMA fight was nearly scrapped this week when his opponent was arrested for a probation violation ... but TMZ has learned organizers have dug up a replacement fighter just in the nick of time.

The fight has been in the works for months ... the ex-WWE champ was slated to get in the ring with Rashid Evans (not the one from the UFC) at a CES MMA event in Providence, Rhode Island.

But a rep for the event tells us ... Evans was scratched from the fight card when he was arrested for violating his probation some time last week ... and once again, it seemed like fate was going to prevent Bautista's MMA career from ever getting started.

Event organizers scrambled to find a replacement fighter -- a guy named Vince Lucero stepped up ... which could be a HUUUUGE problem for Bautista because Lucero has been in more than 40 pro fights.

In fact, Lucero has gone toe-to-toe with a bunch of legitimate MMA studs ... including former UFC Heavyweight champ Tim Sylvia (Sylvia won that fight).

The fight is still scheduled to go down Saturday at 8pm ET.