I got this during the first triple-threat match you come to in the Tecnicos storyline on easy difficulty. I assume it'd work the same if you tried it in a triple-threat Pride match also.
Just don't touch your controller for 5 minutes when the match starts and let the 2 CPU luchadores fight. Don't worry if they start beating you up too - I kept restarting because eventually one would always end up grappling me, and I assumed that it would void the trophy. In the end I just let them beat me up also to see if it'd still unlock, and to my surprise it did! You shouldn't need to worry about anyone being pinned or submitting either, and if they knock you down and go for the pin the other CPU will break it up.
Much easier trophy than I initially thought (without using 2 controllers).