The English champions face Valencia at Stamford Bridge in the first leg after the draw for the last eight and semifinals was made in Athens on Friday.

That will leave Mourinho's men facing a tricky test at the intimidating Mestalla Stadium if they fail to build a significant advantage in London on April 4.

Valencia have won 10 of their 12 home league matches this season and will fancy their chances in the return in Spain on April 10.

But Mourinho said: "For me it is not important. If you play the first game at home some people think the second leg away will be more difficult but sometimes it is more difficult to go away in the first game.

"If you don't win you are under pressure in the second game at home like happened to us against Porto. We got quite a good result in Porto but at half-time at Stamford Bridge we were going out of the competition, so it doesn't matter where the second game is played."

However, Valencia coach Quique Sanchez Flores, whose side are awaiting punishment for the brawl that marred their last 16 win over Inter Milan, believes the draw could have given his side a crucial advantage.

"The best news is that we are playing away in the first leg, which was a priority for us before the draw," he told Valencia's website. "That can be important, and even decisive."

Chelsea will face PSV Eindhoven or Liverpool if they make it past Valencia.

Premiership leaders Manchester United were paired with Roma and boss Sir Alex Ferguson insists he will not underestimate the Serie A side.

Roma may not be regarded as one of the favourites for the tournament, but they are currently second in Serie A and Ferguson believes their surprise win over French champions Lyon in the last 16 shows they must be treated with respect.

"We've never played Roma before so it'll be a new and exciting experience," Ferguson said. "That's the great thing about Europe, you play teams you've never played before.

"We respect their last result (beating Lyon). They have some great players like (Daniele) De Rossi and (Alessandro) Mancini.

"Obviously it's pointless looking beyond this game. We must concentrate on this game only. We're really looking forward to it."

The first leg will be at the Olympic Stadium on April 4 with the return at Old Trafford on April 10. The winners will play AC Milan or Bayern Munich in the semi-finals.

Rafa Benitez has warned Liverpool there must be no repeat of the complacency that led to last year's Champions League exit when they face PSV Eindhoven.

Benitez's side were favourites against Benfica when they met in the last 16 in 2006, but the Portuguese club, then managed by current PSV boss Ronald Koeman, shocked Liverpool with a 3-0 aggregate victory.

Liverpool, who knocked out holders Barcelona in the last round, have already impressed against Dutch league leaders PSV in the group stages this season, winning 2-0 at home and drawing 0-0 in the Netherlands.

The first leg will be at PSV's Philips Stadium on April 3, giving Liverpool the advantage of having the decisive second leg on April 11 in front of their Anfield crowd.

But Benitez is determined Liverpool will not take PSV lightly and he told his club's website: "I'm sure the supporters will be happy with the draw but we don't want to make the same mistake as last year when went out against Benfica. Then, everyone was saying we'd go through but, of course, Benfica beat us home and away.

"At this stage of the competition every team is going to be difficult. We know all about PSV, having already played them twice this season, but that doesn't mean it will be easy.

"Sometimes knowing your opponents well can be an advantage but sometimes it can be a disadvantage because they'll also know all about us. We must be cautious."