Leinster 14 Perpignan - 21:European Cup Semi-Finals: Rugby, said Matt Williams wryly yesterday, has a funny habit of rearing up and biting you in the backside just when you think you have it sorted out. Yesterday's Heineken Cup semi-final at Lansdowne Road was a prime case in point.

From the haunted look on his face, few defeats will have scarred him like this one.

What will gall Leinster more than anything else, after their best campaign ever, is that they didn't remotely play to their capabilities. Man, they're better than this. So much better. Where did the flights of fancy on floodlit Donnybrook Friday nights go? Quite why, only they will know. There were a host of little factors which undermined their performance, and Perpignan applied plenty of spoiling pressure. But at their best Leinster could have coped with that, and imposed themselves. The impression wouldn't go away that the weight of expectancy wore them down.

Ultimately, Leinster were even made to look a little limited, which they're not. Where Munster had mostly a kicking game and no other apparent means of retrieving Saturday's semi-final, Leinster seemed to have no Plan B when taking on Perpignan in midfield didn't work.

Only with the late introduction of Aidan McCullen did Leinster start to vary the points of attack effectively and made some inroads closer in. Dropping the very first ball of the day, and always vulnerable in the air, the French appeared like prime candidates for some Lansdowne Road aerial bombardment. But Leinster don't have much of a kicking game either.

Looking anxious and as is their custom, forcing the pass, Leinster couldn't get into any rhythm or break free. Perpignan pushed up, four, five or even six in a line, cramping the home side for space behind their own gain line. Amid a steady stream of indirect penalties, mostly against Nicolas Mas for boring in at scrum time, this was most obvious from the telegraphed tap penalties to Victor Costello, as Perpignan freely engaged within 10 metres without being penalised additionally until deep into injury time.

With the support ruckers unable to hit the breakdown with any real impact, crucially Leinster struggled for quick ruck ball. Seconds regularly passed as Brian O'Meara had to fish for the ball, so allowing the red and yellow line to comfortably readjust.

Semi-final nerves can rarely have been more in evidence than in the first period here. This was betrayed by a plethora of handling errors, many unforced, though the majority of them were by an equally edgy Perpignan. The tone was set by Ludovic Loustau fumbling the opening kick-off by O'Meara. And so it continued.

Under enormous pressure to reach a final and entertain a typically reactive home crowd, Leinster's mental frailties weren't helped by O'Meara's inability to keep the scoreboard ticking over. As Perpignan lived on the edge, the penalties flowed but for the third competitive game running, his ratio was well below what was required at this level.

Inside the first four minutes O'Meara had missed two three-pointers, the second a bread-and-butter kick from 20 metres out. Though he nailed a well-struck 45 metre effort at the end of the first quarter, he missed another couple by the break, and so all Leinster had to show for the first-half was a meagre 3-0 lead.

With David Quinlan taking the ball up well, and Brian O'Driscoll forever probing and looking for the off-load, as did Christian Warner, it should have been better, but it could easily have been worse. Edmonds himself missed a straightish 40-metre penalty, and soon after Mallier was binned for persistent offside (as much against his team-mates) Edmonds intercepted a delayed pass by O'Meara, Frederic Cermeno hacked on but Denis Hickie showed great strength and pace in saving a seven-pointer.

Hickie's recovering speed has saved Leinster a truckload of points over the past few seasons, but an ensuing intercept by Phil Murphy off Girvan Dempsey's off-load effectively cancelled out Leinster's 10-minute numerical advantage.

Cermeno levelled with a drop goal soon after the restart. O'Meara, after a good, aggressive Leinster lineout maul, regained the lead but Edmonds retorted with a 48-metre drop goal. But then Pascal Bomati made a schoolboyish forward pass (actually, that's unfair to schoolboys) off the restart which Leinster punished with a trademark set-piece try off the scrum. Quinlan passed behind O'Driscoll for Hickie to take Christophe Manas on the outside and draw in Cermeno, for D'Arcy to take his score adroitly. Leinster looked set fair at this point.

However, Edmonds, who had gathered his own deft chip ahead only for Dempsey to block his intended grubber, then rewarded good pressure and strong running by Manas in particular to chip expertly to the corner for Bomati. More worrying still for the crowd was the sight of O'Driscoll being helped off, and in their time of need many of Leinster's fans began heading away in droves.

Though he hit the upright with his conversion, Edmonds duly put Perpignan ahead with an angled penalty after Warner had been obliged to concede an attacking line-out following one of several poor passes by O'Meara. And the canoe was becoming paddleless after Nathan Spooner's high pass to Quinlan conceded territory and Marc Dal Maso rumbled in off a secondary maul from the ensuing line-out.

By the time Spooner landed an injury-time penalty it was desperation stuff. No one stood up to be counted more than Hickie and McCullen in the desperate throes of the end game, the former seeking out gaps, the latter pumping his legs furiously in contact for extra yardage. It failed with knock-ons by D'Arcy and Quinlan. But these things happen when you're playing catch-up.

That wasn't why Leinster left this one behind them.