Saracens boss Mark McCall has described European Champions Cup opponents Toulon as "a dangerous animal" ahead of Saturday's clash at Allianz Park.

McCall's men have already secured a quarter-final place, but victory over the three-time European champions would secure an all-important home draw.

Holders Saracens beat Toulon on the Cote d'Azur three months ago, but McCall knows the degree of difficulty facing his players is considerable in their quest for a repeat performance.

A Toulon win would also take them through - but defeat could spell pool stage elimination.

"It is a massive match," McCall said.

"It's good that we have qualified, but we want to secure a home quarter-final if possible. They (Toulon) have got all their squad back together now.

"Matt Giteau came back last weekend and looked good for the 30 minutes he played, (Josua) Tuisova was devastating for the 20 minutes he was on the pitch, Juan Smith was back for them, so they will come to us thinking they will have a big chance because we are missing a few bodies.

"I know that every player they have is unbelievably competitive, and when they've been asked to step up down the years - when they really need it - they are very tough to play against.

"When they are motivated they really are a dangerous animal.

"It's a huge game at home, and a win gets us what we want. We've got to be very smart with how we play the game."

Saracens have drawn their last two matches (Getty)

Former Bath boss Mike Ford and ex-Leicester rugby director Richard Cockerill are now key figures in the Toulon coaching team, and McCall added: "You can see (Toulon) are a lot more organised than they were, right across the team.

"In the set-piece, in the way they play, and the detail is a lot better than it was a couple of months ago. It's no surprise, as they are good coaches."

Wasps will join Saracens in the knockout phase if, as expected, they beat tournament minnows Zebre on Sunday, but that is likely to be it from an English perspective in terms of quarter-final representation.

England flanker James Haskell will make his first Wasps start of the season after suffering a head knock during a 35-second comeback appearance off the bench following seven months out against Leicester 12 days ago. Danny Cipriani, Kurtley Beale and Tommy Taylor also feature.

Haskell makes his first start after a lengthy injury lay-off (Getty)

"Teams like Zebre will always want to leave a mark in any competition, and if you look through their home games in the PRO12 this season they have nearly caused a few upsets so we will pay them the respect they deserve," Wasps rugby director Dai Young said.

"It is important that we are in the right place, mentally, and our accuracy is good. It's also important that we start strongly and hit the ground running."

Four of the quarter-final places are already filled by Saracens, Munster, Leinster and Clermont Auvergne, and of the other English challengers, potentially only Exeter have a chance of progressing.

The Chiefs, though, realistically need a bonus-point win against Clermont at Stade Marcel-Michelin and must then rely on results elsewhere if they are to hold any hope of matching last season's dramatic final-day qualification. On that occasion, they progressed after claiming a five-point maximum at the Ospreys' expense and Bordeaux-Begles beat Clermont.

Exeter are facing a tough ask to reach the last-eight (Getty)

"It's a scenario that is not too different to that of last season," Exeter head coach Rob Baxter said.

"Yes, we have to do well in the game, we have to have results go our way, but history shows that strange things can happen.

"Getting tied up with points and where we will come will probably only confuse us and cloud exactly how we want to play and what we want to get right. We certainly won't get carried away too much with points and what it will take to qualify.

"The reality is that it is about turning up like we did last weekend against Ulster and putting in levels of performance that deserve to win the game."

Elsewhere on Saturday, Glasgow will book a first-ever Champions Cup quarter-final place if they beat Leicester at Welford Road, while Munster can prepare for a home tie later this season with a home win over Racing 92.