Mike Catt has lost his fitness battle for London Irish's Heineken Cup semi-final against Toulouse at Twickenham. Catt is suffering from a recurring nerve-related problem that affects his hamstring and calf.

Catt, who played a key role when Irish beat quarter-final opponents Perpignan, missed last weekend's English Premiership victory over Harlequins.

And Irish boss Brian Smith has opted for the same midfield trio that started against Quins, with Shane Geraghty at outhalf and England scrum-half Peter Richards being joined by centre partner Seilala Mapusua.

Catt and prop Clarke Dermody (leg) both failed fitness tests ahead of Irish's first Heineken semi-final appearance. Two changes from the Quins clash are both up-front, where lock Nick Kennedy and number eight Phil Murphy return to starting duty.

Smith said: "The squad has worked hard through this season's pool stage, and played with great control and intelligence in beating Perpignan in the quarter-final.

"Tomorrow requires another step-up in performance."

London Irish: P Hewat; T Ojo, P Richards, S Mapusua, S Tagicakibau; S Geraghty, P Hodgson; D Murphy, D Paice, F Rautenbach, N Kennedy, B Casey (capt), D Danaher, S Armitage, P Murphy. Replacements: T Lea'aetoa, S Mackie, J Hudson, R Thorpe, J Leguizamon, N Mordt, E Hickey.

Toulouse: C Heymans; M Medard, M Ahotaeiloa, Y Jauzion, Y Donguy; J-B Elissalde, B Kelleher; D Human, W Servat, S Perugini, F Pelous (capt), P Albacete, J Bouilhou, Y Nyanga, S Sowerby. Replacements: A Vernat Basualdo, O Hasan, R Millo-Chluski, G Lamboley, M Mermoz or V Courrent, M Mermoz or T Dusautoir, F Maka.