Elissalde manages to cramp Geraghty's style in the sunshine

It is human nature to wish that big matches – semi-finals and finals – are contested at full stadiums by two squads of fit players in their pomp, but this was not so much the survival of the fittest as a battle between the least unfit.

Toulouse were so assailed by injuries that they included six forwards on the bench, among them Thierry Dusautoir, who had originally been excluded in order to continue grieving his late father. Irish were missing the ageing muse in their backline, Mike Catt, which left much responsibility on the 21-year-old shoulders of Shane Geraghty, the fly-half only recently restored to the side after six weeks out with knee ligament trouble. Toulouse defied conventional wisdom by picking a No 9, Jean-Baptiste Elissalde, at No 10 and he had to play half the match with a heavily strapped knee. Rarely has a win come with so much of a wince.

As a spectacle it might have been Twickenham Lite, with only the bottom tier of seating required, had it not been for the dancing, drum-beating supporters from Toulouse and the players' whole-hearted efforts to entertain them. There was a banner in the South Stand which translated as "Vincent we are with you", in commiseration with the French side's wing, Vincent Clerc, who tore knee ligaments last weekend. If the fans had brought a placard for every crocked Toulousain they would have stretched around the ground.

The three-times European champions had only one back in reserve. When Elissalde had his right knee bandaged up with 36 minutes gone it was yet another worry. He was well enough to kick his second penalty goal immediately afterwards and two more in the third quarter to open up what proved a decisive six-point gap.

With Irish deploying an apparently more comfortable playmaker in Geraghty, it was a fascinating contrast all the way through. You would guess that what pops most readily into Elissalde's mind would be a pass or a box-kick so that, moved one position out, he would be unsure when or whether to do either. On three or four occasions he fell between those two stools and came up with cross-kicks which were not totally ineffective but looked unnatural.

Geraghty, an instinctive runner, waited ages to show his wares. He often stood in the centres, with the hefty Seilala Mapusua inside him at first receiver to handle the rough stuff, and concentrated on throwing passes so flat they were almost at right angles to the touchline.

It worked, to the extent that the wings, Sailosi Tagicakibau and Topsy Ojo, made hay in the south-west London sunshine: a try apiece before and after half-time, albeit with awful tackling from the Toulouse back three. As it all unfolded, Catt (Geraghty's mentor) and Toulouse's head coach, Guy Novès, crouched pitchside, each hugging an advertising hoarding. Handy product placement, that.

Geraghty is the London Irishman with a dash of Mayo – the county, that is, where his father was born – though the son hails from Coventry. The dash which so nearly warmed the cockles of the Exiles' hearts, not to mention the mussels, came on 72 minutes. Standing deep behind a line-out, Geraghty shrugged off Dusautoir and got away from a front-rower or two and into clear water. Here at last were shades of Twickenham a year ago, against the French in the Six Nations, when Geraghty's vivacious performance off the bench promised international riches so far largely untapped due to injuries in the meantime.

The Toulouse defenders mustered on their 22 like the parting of the red sea in reverse, and Geraghty shaped to unload the killer pass. He needed the supporting Tagicakibau only to run a straighter line; the Samoan may have judged he would be covered if he got too close. On such split-second decisions are semi-finals won and lost.

Still trailing by six points, and with the final whistle imminent, Irish had to keep running. Trouble was, Geraghty was down getting treatment for cramp; he hopped up to throw the tiredest of passes which was almost intercepted by Yves Donguy. It was over, in any case. Geraghty will keep learning; Elissalde and Toulouse have the final to look forward to.