Cardiff captain Rob Howley accepts his side have it all to do as they host Toulouse in the Heineken Cup on Saturday.

After a costly loss to Ulster in their opeing European tie against Ulster another slip up will all but severely hinder their chances of progressing to the later stages.

If, as expected, group leaders Saracens beat Ulster on Sunday, then tomorrow's Arms Park losers will find themselves cut dangerously adrift with little hope of a quarter-final place.

And Howley, caretaker skipper in the continuing absence of injured Wales prop David Young, knows what is at stake.

"It will be a mammoth task for us to go and beat Toulouse or Saracens away from home, so we have to win tomorrow," he said.

"Hopefully, with a packed house at the Arms Park, we can produce a good enough performance to win the game, but it is a mountain to climb."

A handling blunder by Wales full-back Rhys Williams gifted Ulster their surprise win, and Howley admits that it was a match Cardiff had targeted to win.

"It looked on paper as if Ulster would be one of the weaker sides in our group, and to be honest, we expected to win," he added.

"To become a force in the pool, we needed to win, but we made too many unforced errors, and you cannot do that in this standard of competition."

Howley has produced glimpses of world-class form this term, a timely return to his best after being dropped by Wales coach Graham Henry last season.

He also lost the national captaincy to Young, but a starring role against Toulouse could underline his claims for a recall when Samoa arrive at the Millennium Stadium for the first of Wales' autumn Tests on November 11.

Yet even if Cardiff and Howley topple Toulouse, then there is a danger of them becoming embroiled in a furious row with Heineken Cup organisers.

Cardiff officials have still refused to rule out selecting Wales prop Peter Rogers, despite European Rugby Cup Limited claiming he is ineligible.

It is understood that Rogers' name has been included among the Cardiff team printed in tomorrow's match programme.

But ERC say he cannot play because he had already been registered with his former club Newport for this season's Heineken Cup, and joined Cardiff almost a week after the September 26 registration cut-off date.

Cardiff's board of directors remained tight-lipped after discussing the matter last night, but if Rogers plays, then there could be far-reaching consequences.

Rogers' would clearly help Cardiff combat the scrummaging threat of Toulouse's French international tighthead Franck Tournaire, yet it hardly seems a risk worth taking.

Toulouse, meanwhile, who won the Heineken Cup at Cardiff's expense in 1996, must bounce back from last weekend's home defeat against a Thomas Castaignede-inspired Saracens outfit.

And coach Guy Noves admits that the intensity of Saracens' performance caught his players off-guard.

"I have to admit that we were not prepared for the step-up in intensity of the Heineken Cup," he said.

"We only played three French Championship games before going into Europe, and the pace of those matches is limited compared to Heineken Cup rugby.

"We are playing catch-up to the English clubs in terms of match fitness, but we also made mistakes that you cannot afford against a side of Saracens' calibre.

"Cardiff will be disappointed not to have come away from Ulster with a win, but we are not concentrating too much on their game," he added.

"Whoever you play in this tournament, you take them seriously, and even if both ourselves and Cardiff had won last weekend, then this would still be a very tough encounter."