Conor McGregor disagreed with the judges' decision which saw Katie Taylor lose to Chantelle Cameron on Saturday night.
The fight, shown live on DAZN, was scored 96-94 in Cameron's favour twice, with the other judging calling it a draw.
A draw would have seen Cameron retain her belts as the incumbent, but many observers felt that the English fighter was the worthy winner regardless.
Her 36-year-old Irish opponent wants an Autumn rematch according to her promoter Eddie Hearn, and McGregor quibbled with the final result.
McGregor told BBC Radio 5 Live: "Sport won tonight, it was a great one. A very close fight. Katie went up a weight at the drop of a hat to make this event happen. She didn't have time to build up to the weight. She took a chance."
"We had it a draw there. The nerves at the start of the fight set her back. She wasn't Katie at the start. She was Katie from midway on when she started to come on into her own. Close fight but I'd call it a draw."
McGregor had been supporting his compatriot in her first professional fight in Ireland in a long-awaited homecoming match-up.