London Irish will go into their first Heineken Cup semi-final, against Toulouse at Twickenham tomorrow, without Mike Catt, their most experienced player. The former England captain, who played for Bath in their 1998 European triumph over Brive, has been struggling with a damaged right calf and will miss the biggest day in the exiles’ professional history.

Although they will not confirm their starting XV until today, the likelihood is that London Irish will field Peter Richards at centre alongside Seilala Mapusua, with Shane Geraghty at fly half — the midfield that did duty in last weekend’s Guinness Premiership win over Harlequins.

London Irish will miss Catt’s calculating brain, but they will want to give the elusive Geraghty his head in a game that Toby Booth, the forwards coach, describes as “good over evil”. This is not a disparaging comment on Toulouse, three times European champions, but his description of an encounter when attack should dominate over defence because both teams are committed to flowing rugby.

Whether Toulouse’s commitment in this respect is as absolute as usual remains to be seen. Their squad of 24 contains only nine backs, of whom Valentin Courrent, who can play either half-back position, is a doubt with a damaged thigh. In that case the French club will name only one replacement back, probably Maxime Mermoz, and six forwards, so badly affected have they been by injuries.

Nor will they make a decision over Thierry Dusautoir until the last moment. The flanker, who was brilliant in France’s World Cup campaign last autumn, was shaken in a collision during last weekend’s defeat by Clermont Auvergne and suffered the death of his father this week.

Alex King, the former London Wasps fly half who is now with Clermont, has pinpointed Jean-Baptiste Elissalde as a potential weak link in the Toulouse back division. Elissalde played fly half rather than his normal scrum-half position last weekend and was unable to ignite his threequarter line, but London Irish will assume that, on the counter, Toulouse remain as dangerous as ever.

“You can look at tapes until you’re blue in the face,” Booth, who will coach England Saxons in their defence of the Churchill Cup in June, said. “But you’ve also got to look at what you can control. If you worry too much about what the opposition do, you may suppress what you can do.”

Munster will select from a full hand for Sunday’s semi-final against Saracens at the Ricoh Arena in Coventry in the expectation that the knee injury suffered by Ronan O’Gara, the Ireland fly half, has cleared.

Bristol have signed Junior Fatialofa, the 27-year-old near 17-stone centre, from Exeter Chiefs.

After a disappointing season in the Guinness Premiership, Worcester Warriors are two games away from qualifying for next season’s Heineken Cup. In this evening’s European Challenge Cup semi-final they face Newcastle Falcons at Sixways. The visiting team, who welcome back Jonny Wilkinson, Toby Flood and Jamie Noon, have lost their past seven league games. Mike Ruddock, the Worcester director of rugby, can recall Pat Sanderson and Dale Rasmussen after injury. The winners face Bath or Sale Sharks.