Toulon can cook Saracens' goose by battering Castres

The French side can end Saracen's Challenge Cup bid with a bonus-point victory

This Challenge Cup lark was supposed to be easy. In the four completed campaigns since 2005-06, 15 of the 20 round-robin pools were won by English clubs, who also filled 19 of the 32 quarter-final places.

Only Clermont Auvergne, far from the weakest team in France, managed to break the Premiership's stranglehold on the competition by beating Bath to the title in 2007. For all the changes this season – a fresh title sponsor in Amlin, a new football-style format allowing only the group winners to proceed to the knock-out stage – the trend was certain to continue. Wasn't it?

Not so. Not by a long chalk. If Wasps tied up their group with a match to spare – just as well, given their defeat in Paris on Thursday night – Newcastle were playing for their future in the tournament at Kingston Park yesterday evening while Worcester disappeared over the cliff long ago.

As for Saracens and Leeds, the next 24 hours will be decisive. The former are under serious threat from Philippe Saint-André, Jonny Wilkinson and the rest of the expensively accumulated bunch at Toulon, while the latter find themselves facing a winner-take-all argument with Bourgoin.

Saracens will no doubt put a shedload of tries past Rovigo in the Veneto this afternoon: the overmatched Italians have conceded well over 250 points in their five outings to date and are most unlikely to improve their average against opponents boasting full internationals from around the globe and uncapped players as hot as Andy Saull, the fast-improving young English flanker.

However, Toulon are ahead of Brendan Venter's side by a point and play Castres on the shores of the Mediterranean tonight. If they win with four tries, as they ought against a team with next to no interest in the fixture, Saracens' goose will be cooked. There are no complications surrounding the Leeds-Bourgoin game at Headingley tomorrow.

Both sides are on 19 points, so victory is everything. The Yorkshiremen have scored more freely than their opponents over the course of the competition and with four first-choice forwards back in the pack – Mike MacDonald and Juan Gomez return to the front row, the in-form Erik Lund starts at lock and Kearnan Myall resumes on the blind-side flank – they have enough in the way of old-fashioned "grunt" to absorb whatever strong-arm pressure their visitors might inflict.

But Bourgoin are taking this sufficiently seriously to include their most prized possession, the goal-kicking outside-half Benjamin Boyet, and can be expected to pose a threat. "The old adage that French teams struggle away from home is no longer true," asserted Andy Key, the Leeds director of rugby, yesterday. "With the extra exposure to overseas games via the European competitions, teams have become accustomed to the demands placed on them by travelling."

Bourgoin frequently seem intent on doing everything in their power to contradict Key's argument. But they reached the final of this tournament last season, winning a last-eight tie at London Irish along the way. That alone makes them dangerous.