The Dubliner sparred with Chris Van Heerden last year
Conor McGregor and Floyd Mayweather are to meet in a highly anticipated cross-over boxing fight in August.
The bout has been derided by many who see it as a money-grab in what should be a procession for the unbeaten Mayweather.
McGregor sparred with South African contender Chris Van Heerden last year as he prepared for his rematch with Nate Diaz at UFC 202.
After the announcement of the "mega-fight" between the Irishman and the unbeaten American, the South African released footage of his training sessions with McGregor.
People telling me Mayweather will have his hands full trying to land on McGregor -STOP IT! I respect McGregor BUT i ain't Floyd and i landed pic.twitter.com/gd4dFi3XUU— Chris van Heerden (@TheHeat001) June 14, 2017
The footage will do little to quell fears that August's bout will be nothing more than a lopsided blow-out in Mayweather's favour.
Van Heerden is relatively unheralded in boxing circles and his most notable fight was a TKO defeat to Erroll Spence Junior in 2015.
McGregor has never had a professional boxing fight in his career while Mayweather is regarded as the greatest defensive fighter to ever lace gloves.
With a record of 49-0, the Las Vegas-based boxer has seen off this era's best including Manny Pacquiao, Miguel Cotto and Saul Alvarez.