GLASGOW will have to put on the performance of their lives if they are to prolong their European adventure, Gregor Townsend has confessed.

Warriors are looking forward to their first Champions Cup quarter-final against reigning champions Saracens on Sunday.

But fired-up head coach Townsend does not believe his team should be happy to make up the numbers at Allianz Park and reckons they can upset the Londoners.

However, he warned his players none of them can afford an off-day if they are to shock a side who have gone 15 games in Europe without defeat.

The Scotstoun boss said: "It's a huge game. To play at this stage of the competition is a first for this club - but it's a quarter-final. You want to get to finals and to win tournaments.

"We're in a position where we can now do that but we have to deliver our best ever game.

"I believe we're in the right place to do that having looked at the way the players have trained and their fitness levels.

"But we do know we're up against a team who do make it very hard to play your best game.

"This is a high-level game - the closest you will get to Test match rugby.

"They are an excellent side who get a lot of things right, starting with their culture. Their guys all buy into their game plan and work very hard for each other.

"They are hugely successful and have been excellent in Europe the last couple of seasons and that's down to their consistency.

"When you look at their players they have some brilliant individuals. Guys who will be starting Lions Tests come the summer.

"We respect them very highly, so it's a brilliant challenge for us to go up against what's realistically the best team in Europe."

Around 5,000 Glasgow fans are making the trip south but they will fear there will be little their side can do if Sarries perform to their maximum.

But Townsend, who has recalled nine of his Scotland internationals for the weekend showdown, reckons his side can make life uncomfortable for Mark McCall's men.

"We have to make them have an off-day," he said. "If you are playing well and scoring tries, making breaks and defending well, the other team will tend to look at what they are doing which isn't working well.

"Maybe they have not passed the ball as well or defended so good. So what you do with your performance forces the other side not to play so well.

"There are not many games where both teams play to their real best. Our game against Munster this year was close to that and that is what we're expecting this weekend - a really good Saracens team playing at the top of their game - but we still believe we can win this Sunday."

Warriors will be boosted by the return of their Dark Blues contingent, including co-captains Jonny Gray and Henry Pyrgos.

Scrum-half Pyrgos will be partnered by stand-off Finn Russell, while Peter Horne is paired alongside Alex Dunbar in the centre.

On the wings, Tommy Seymour and Lee Jones both return and Stuart Hogg retains his place at full-back to complete the back three.

It is a familiar front row, with Gordon Reid, Fraser Brown and Zander Fagerson combining several times for Scotland during the RBS 6 Nations.

Gray partners Brian Alainu'uese in the second row, while Ryan Wilson wears number seven, joining Rob Harley and Adam Ashe at the back of the scrum.