Mackintosh was sent from the field in the 25th minute of the game on Saturday night after his elbow went into the face of Otago prop Hisa Sasagi, when Mackintosh was trying to put defensive pressure on the Otago inside backs.
The man they call Whopper felt the ordering off was tough and had a big impact on his team.
''I let my mates down. It was not my intention at all. I just got checked. He ran into me,'' Mackintosh said.
''At the end of the day I'm embarrassed. It is a red card. I would have loved it to go upstairs. I just wanted to have a look at it. I didn't punch someone in the head. But he [referee Jamie Nutbrown] had made his mind up.
''I don't want to be remembered for stuff like that. It was a major turning point in the game and we never recovered from it.''
''It was a pretty reactionary thing. It probably deserved a yellow but I didn't think it deserved a red. I said to him before he pulled out the red card, 'can you have a look at the big screen?'
''He came up to me and said I had punched him in the face. But I had certainly not done that.''
The former Highlander said losing a player had a huge impact on any side, although he said Otago played very well.
''It's not as though I dragged someone out of a ruck and punched them in the head.''
He did not see himself as a dirty player and the elbow was reactionary.
It was the first red card he had received in a long career, he said.
Otago coach Cory Brown said the loss of a man from a side did possibly have an impact on the game and the scoreline.
It was a silly thing for Mackintosh to do, but Otago was already on top when the incident happened, the Otago coach said.
Otago was up 20-7 when Mackintosh was sent from the field.
