Referee Marius van der Westhuizen sent Richie Mo'unga off the field in the 73rd minute when he was told the Crusaders had used all eight of their replacements and the flyhalf's return for the injured Mitchell Hunt was illegal.
The Crusaders players and officials were left dumbfounded by the decision and were heard on television telling the match officials they believed Hunt had left the field for a Head Injury Assessment (HIA).
Match officials, however, said Hunt had suffered another injury and therefore could not be replaced.
The Crusaders conceded a late try to Scott Higginbotham while being a man down but managed to hold on for the win in the face of a furious fightback by the Reds.
"The guy on the sideline said Richie had to come off and we said 'no, because it was HIA (to Hunt)," Robertson told Stuff Media on Sunday over the near farcical scenario.
"It was pretty clear that Mitch Hunt wobbled coming off, so he had the head knock.
"He didn't even go for an HIA check. They believed he was knocked out, so it was just straight off. That is where the confusion started (amongst the officials), we believe.
"Afterwards we got an apology, which is a bit late.
"There are some protocols around this, and our manager Shane Fletcher will go through the right process to get some clarity and see how that ends up."
The Crusaders, who have won the last two titles, lead the points table after three successive victories and host the winless Waikato Chiefs in Christchurch next Saturday.
(Reporting by Greg Stutchbury; Editing by Sudipto Ganguly)
