Dan McFarland says Ulster's one-point aggregate defeat by Toulouse did not come down solely to Tom O'Toole's red card, but a number of key moments.

Antoine Dupont's converted try with five minutes left sent the defending champions into the last eight.

"Ultimately the game is decided because we did a couple of critical things that were wrong," McFarland said.

"Teams do that obviously, but if you want to win at this level against sides of the quality of Toulouse you can't afford to make those mistakes.

"It happens but just on the day we didn't quite get right."

Ulster brought a 26-20 advantage into their home leg, having secured a memorable win out in Toulouse after the French champions had been reduced to 14 men in the 10th minute.

However, that lead was wiped out before the half-hour mark in Belfast as the visitors scored two tries in quick succession - the first from Thomas Ramos after Romain Ntamack seared through Ulster's defence before the fly-half ran the length of the field for an intercept score five minutes later.

"I look at their two tries, like we gifted them two tries. A poor piece of defence let them through on the inside shoulder and an intercept pass in the space of five minutes," reflected McFarland.

"There was another critical call on James Hume off his feet at a breakdown and that was to me just not a penalty at all. That was another critical moment.

"When you watch their half-backs work and the quality of their play. Dupont is kicking the ball from literally under his own posts to 45 metres from his own line.

"We were piling pressure on them there and he does it regularly. It's just next level and that's what you can expect from the best player in the world."

After O'Toole's was shown red for a high hit on Anthony Jelonch, Ulster extended their lead through a John Cooney penalty before Toulouse worked their way up the field and patiently waited for space to open that would eventually allow Dupont in for the decisive score - the visitors winning the match 30-23 and the tie 50-49 on aggregare.

"Their try at the end obviously came off the back of having an extra man and being so potent, being able to stretch the field like they do," accepted McFarland.

"You could pick out any moment from the games. We gave a try away because we gave up an inside shoulder in defence. If we don't do that, that's not a try.

"Last week if the tackle area had been a little bit clearer, [referee] Wayne Barnes maybe would have given us the jackal penalty that would have meant we were 13 points up going into this leg.

"There are instances across the board. Equally there was probably a forward pass in the lead-up to one of our tries. There are plenty of things in the last two weeks that if we had done better we would have won but in the end it is what it is.

"We could have won it if we had been a little bit sharper in a couple of areas I'd expect us to be sharper in.

"We didn't quite get it right, but the margins are so small against a team like Toulouse, you're living on the edge the whole time and if you get anything wrong they're going to punish you."