Hibernian boss Mixu Paatelainen was furious with Hearts captain Christophe Berra following Steven Fletcher's sending off.
Fletcher was red carded following his late tackle on Berra during Hibernian's 2-0 defeat to their city rivals at Easter Road in their fourth round Scottish Cup tie.
Goals from Christian Nade and substitute Gary Glen helped Hearts to victory, but Paatelainen is convinced the sending off of Fletcher was the turning point in the game.
"My opinion doesn't count but it was never a sending-off," fumed Paatelainen.
"Fletcher's foot touched the ground and he did not catch Berra at all. However, Berra jumps like a brown trout and makes things worse for Fletcher.
Disappointed"So I'm disappointed that Fletcher got sent off for nothing and that changed the game.
"If there is a challenge like that when strikers close down defenders, sometimes they go in a little bit late.
"You can see if the striker goes for the ankle, the shin or over the ball and wants to harm the player.
"But there was nothing like that in that situation at all, you saw it clearly on television.
"I don't think it was even worth a yellow.
"If the official felt it was dangerous or too much power was used then maybe it was worth a yellow but definitely not a red."
"I'm massively disappointed," Paatelainen continued.
"We started the game well, passed the ball well and totally dominated. We could have, should have, and might have scored before the turning point.
"I told the boys that I was delighted with the way we started the game. At 11 versus 11 we were far the better team."
Hearts boss Csaba Laszlo tried to diffuse the situation by saying: "I can understand the emotions.
"If you lose 2-0 at home then you search for something.
"But if he had not been sent off we might have gone on to win 3-0, who knows, anything in football is possible.
Aggression"I saw a lot of aggression from the Hibs players and there was also a challenge on Ruben Palazuelos (by Lewis Stevenson).
"It was a difficult game for the referee but he handled it well."
Despite beating their arch-rivals, Laszlo was far from happy with his side's showing.
"I saw a lot of things in my team that made me unhappy," added Laszlo.
"I was not happy with 2-0, I would not have been happy unless it was 4-0.
"We were dribbling five yards from goal. This is serious work and I can't accept that."
Laszlo looked forward to the visit of Falkirk in the next round.
"We lost on penalties to Airdrie in the League Cup so we have had no luck with smaller teams," he said.
"Maybe it's best to have a team from the SPL, that might make it easier for us."
The Hearts boss is hoping goalkeeper Janos Balogh will make his loan deal permanent.
The keeper is set to return to Hungarian side Debrecen next week after six months at Tynecastle.
Laszlo said: "We will need to decide in the next week.
"But if the two clubs don't come to an agreement then he must go back."