Saracens have changed half their pack from the Premiership defeat by Bristol as they face up to what the club is calling "the biggest game of the season so far" in the Heineken Cup against Biarritz at on Saturday.

Victory at Vicarage Road will go a long way to Sarries securing a place in the quarter-finals of the tournament for the first time in the club's history, while the Basque visitors know they must win or face being knocked out of the competition.

Saracens' director of rugby Alan Gaffney shuffles his forward pack with recalls for props Cencus Johnston and Nick Lloyd, lock Hugh Vyvyan and flanker Kris Chesney while the only change in the backline sees Richard Haughton return to the starting fifteen.

"The equations are pretty simple on Saturday," said Gaffney. "If we win we have a great chance of making the quarter-finals while Biarritz know they have to win or face being knocked out of the tournament.

"But we know they have a quality team who can get results. We outscored them three tries to one in our match earlier in the campaign in France but they played to their strengths and won with the last kick of the game.

"Looking at their history in the competition, you see that they have made the knockout stages in six out of the last seven Heineken Cups which says much about their quality.

"However, we go into the game knowing our destiny is in our own hands and that's all we can ask for.

"From our perspective, we've had a positive week in training and the guys will be going into the match very upbeat and looking forward to what should be an excellent game. It's a huge match."

Saracens team, v Biarritz, Saturday:

15 Brent Russell
14 Richard Haughton
13 Kevin Sorrell
12 Andy Farrell
11 Rodd Penney
10 Glen Jackson
9 Neil de Kock (capt)

1 Nick Lloyd
2 Fabio Ongaro
3 Cencus Johnston
4 Hugh Vyvyan
5 Chris Jack
6 Kris Chesney
7 Richard Hill
8 Ben Skirving

Replacements:
16 Andy Kyriacou
17 Tom Mercey
18 Tom Ryder
19 Paul Gustard
20 Alan Dickens
21 Adam Powell
22 Kameli Ratuvou