Australia coach Don Abnett was left gobsmacked by a decision which denied tear-drenched Aussie teenager Jai Opetaia the biggest boxing upset of the London Olympics.

On a forgetful night when the Aussies went 0-3 in the ring, heavyweight Opetaia took it to Azerbaijan's world No.1 Teymur Mammadov only to come up one point short in a 12-11 loss.

While the 17-year-old Opetaia, Australian boxing's youngest ever Olympian, refused to criticize the judges, Abnett let fly.

"It was 9-9 going into the last round, I had him three points up about a minute into the third round - that didn't change," Abnett said.

"His opponent didn't score any points and Jai didn't score any more.

"How five judges sitting around a ring could get that wrong is beyond me.

"When we went out to the dressing room every country comes up to us and tells us the same.

"For a 17-year-old boy to come and fight his bum off and not get the decision he deserves - it's shattering."

Opetaia, a cousin of Socceroo Tim Cahill, was too distraught to speak immediately after the fight and when he returned a short time later the tears were still flowing.

Disappointed, he refused to dwell on the manner of his loss and instead turned his attention to making amends in Rio de Janeiro in 2016.

"I'm just devastated, devastated," Opetaia told AAP.

"I thought I fought really well, but it's up to the judges and they didn't give it to me.

"This is just the stepping stone to where I want to go - the next step is Rio.

"Four years - I've got four years to get faster, stronger.

"I'm going for the gold medal in 2016."

But bantamweight Ibrahim Balla was less forgiving after he lost a controversial bout to Bulgarian Detelin Dalakliev, whom he labelled a coward after the fight.

Balla went down 14-10 that included a last round loss of 6-3.

"How can you be down in the last round when you throw two times, three times as many punches as the other guy and he runs away like a coward," Balla said.

"The scoring system, I'm not happy with it today.

"I definitely thought going into the last round one down I thought I pulled it off."

In Australia's last fight of the night, the judges didn't get a chance to make a decision when super heavyweight Johan Linde was floored with a left hook just two minutes and 14 seconds into the second round.

It ended a dismal day for Australia's boxers at the Olympics.