Glen Jackson insists Saracens can gain revenge against Ospreys and book a place in the semi-final of the Heineken Cup. Ospreys, boasting the bulk of the Wales Grand Slam team, hammered Saracens 30-3 in the last four of the EDF Energy Cup two weeks ago. But Jackson is adamant that doubters who say his side face mission impossible on Sunday have got it wrong.

The fly-half is taking heart from a full house at Vicarage Road, believing home advantage and the confidence generated by a 66-7 hammering of Leeds last week will help Sarries upset the odds.

"We had a meeting after the Ospreys defeat and vowed to get the excitement back into our rugby and we saw the immediate response with 10 tries against Leeds," said Jackson. "We didn't give Ospreys much of a game in Cardiff and that was very frustrating given the way we have played all season.

"It's not impossible to turn things around against Ospreys and we need to play like the 'real' Sarries. I finished last season as the top points scorer in England but the team didn't win anything.

"I would swap being top again for a trophy this time because I don't want to be drinking a celebration beer on my own again."

Wales lock Ian Gough is a key man in the Ospreys pack and is wary of his side being the victim of a backlash.

"Winning such a big game by close to 30 points is a massive boost to our confidence, but it also gives Saracens plenty of motivation as well," said Gough. "They wanted to win that game just as much as we did so they will be hurt - they will be looking to really up their game and restore some pride."

Both teams have a key player missing through injury - Saracens will be without All Blacks lock Chris Jack and the Ospreys No9 Mike Phillips.

It's a critical club rugby weekend for the capital with London Irish hosting Perpignan in another quarter-final at Reading tomorrow. London Irish topped Pool One ahead of Perpignan, courtesy of two more bonus points, but Percy Montgomery believes his French side have hit top form at just the right time.

"I don't think the fact that we have already played each other twice this season will mean much on the day," said Montgomery, who kicked 12 of South Africa's points in their 15-6 World Cup Final win over England last year. "Because it's a quarter-final both teams will play as if it is an all-or-nothing final. We had a tough start to the season but we are starting to get some momentum going."