"We're certainly very aware of the of the sort of challenge Ulster will provide and recognise the quality they have in their squad." he said this afternoon.
"To come out of the group they were in was one thing, but to produce the performances, they did especially that win over Leicester Tigers in Ravenhill, shows exactly what a good side they are. I thought they were absolutely sensational that day. One of the best performances we've seen in the campaign this year.
"And they backed that up with their performance at the weekend in Clermont." he continued. "It indicates they are comfortable on the road and wont be at all fazed by having to travel for the quarters.
"But that's some time off. There's internationals to be played, RaboDirect PRO12 matches so we'll see how players come through that phase of the season before turning our attention back to Heineken Cup."
McGahan's skipper Paul O'Connell was equally impressed by this Ulster team. " They were outstanding, against Leicester, and although I haven't seen their game against Clermont, to come away with a point, to get out of a group like that, says it all.
"They've a lot of quality players. A lot of players showing really good form. So it's going to be a really tough game."