Melbourne Rebels captain James O'Connor has labelled a reversed penalty from the television match official (TMO) as a "game changer" when his team were on attack in the second half of their loss against Queensland Reds at AAMI Park in Melbourne.

Reds skipper James Slipper said he asked the referee to go to the TMO because he saw flying boots and the distressed reaction of his teammate Albert Anae. He wasn't aware at the time that the TMO could recommend the penalty be reversed.

The Rebels trailed by seven points at the time and were enjoying good momentum, with O'Connor set to line up a penalty shot that could have put his side only four points behind, but the TMO ruled that Rebels hooker Ged Robinson had been guilty of reckless use of his foot on Anae in the ruck.

Argentina referee Francisco Pastrana passed on the ruling from the TMO to jeers from the Melbourne crowd, and the Reds completely turned the momentum around and almost had a try to Digby Ioane just minutes later.

Rebels captain O'Connor described the reversed penalty as a "game-changer'' but said his team needed to show better composure in the final 10 minutes.

"It was definitely a game changer but it's the ref's call," O'Connor said. "Unfortunately we lost our way after that and they were attacking our line. They were pretty clinical and won the game.''

While that one went their way, Reds director of coaching Ewen McKenzie was furious with the steady penalty count against his team, although the final total was 10-8.

"It's pretty hard to play when we were getting penalised in attack and defence,'' McKenzie said. "At one stage, it was 10-2,'' he said of the penalties. We played maybe 20 phases at the end of the game in the attacking quarter and we still got penalised.''

While bitterly disappointed to lose another match after leading at halftime, Melbourne Rebels coach Damien Hill preferred to look at the positives.

"The second half was a really good tussle,'' Hill said. "The effort for 30 minutes in that second half was outstanding. If we're going to take anything out of this, there was 70 minutes I was exceptionally proud of the boys and it shows we're getting closer.''