Leapai was destroying Nigerian scrapper Izonritei through the opening rounds and a finish seemed all but certain.
With his opponent covering up against the ropes as he searched for the knockout blow in the third round, Leapai opened up a huge cut over Izonritei's eye.
The referee stopped the action and ruled the cut had been opened by a stray elbow.
Leapai, who fought Wladimir Klitschko three years ago, thought he'd won the fight, but it was called a technical draw because the bout hadn't yet reached the fourth round.
If the head clash had occurred after the fourth round, we would have gone to the scorecards.
The 38-year-old was furious after the decision was announced.
"We've got to fix this up," he fumed.
"This is - I could say a swear word - but this is wrong.
"I dominated in the first two rounds and I knew I was going to dominate in this third round and take him out.
"Come on, ref, you've gotta get your sh*t right, man. We're not doing kickboxing here. We're boxing here.
"This won't stop me. I'm still going to make it to the top and if I have to fight him again so be it.
"But there's going to be a rematch because this is bull mate."