The Stormers were brave, defiant but ultimately too ill-disciplined to win in Dublin on Saturday.Leinster, 20-11 victors, will play the Bulls in the United Rugby Championship final at the Aviva Stadium on the 20thJune.The Stormers were always underdogs given the venue and injury tribulations. For the opening 15 minutes Leinster played with the urgency and intensity of defending champions.Somehow, the Stormers hung in there, absorbing attack after attack as Leinster kept coming.The statistics were barely believable in the first quarter. Leinster had 85% possession and 84% field position. Yet the score was just 7-0 to them.The Stormers, in this most daunting opening period, had two set-piece opportunities. They lost a lineout and were penalised at the scrum. But they refused to go away, and these heroics were consistent with what has defined this team since the inception of the URC five seasons ago.For all the individual defensive plaudits, the Stormers’ error rate ultimately sealed their fate.To win play-off matches away from home, the most important statistic is how many unforced errors are conceded. For the Stormers it was too many.They trailed by just five points at the break, 13-8. When Paul de Villiers won another turnover penalty within a minute of the restart, the first-half error rate transferred into the second half.The touch kick from the penalty was missed and the Stormers were immediately under pressure in their own half, defending wave after wave of Leinster attack.Leinster has built a fortress at the Aviva Stadium in big games, but as confident as they were in those opening 15 minutes, they’re not the convincing team of three seasons ago.They started with 15 internationals and had19 Test players in their match 23. If matches are determined on Test caps and on paper, then Leinster should have won by 30.Fortunately, the contest happens on grass, most of the time, and the Stormers brought mongrel and pride to the contest.Leinster struggled with the abrasive nature of the Stormers, but just when it seemed they had exhausted Leinster’s ambition, the visitors gifted the home team a one-player advantage through ill-discipline.Left wing Leolin Zas was penalised and carded for a deliberate intercept attempt in the 45th minute. It was a poor decision, but it mirrored so many big play-off moments that influenced the flow of the match and halted Stormers’ momentum.De Villiers, a specialist jackal to the ball, enhanced his national aspirations. He has a particular gift and his skill set will complement the depth of the Springboks loose forward and the variety in combination choices. It was baffling that they substituted him in the 60th minute.Damian Willemse, at full back, is finding his best form and will be the favourite to wear the Boks’ No 15 in the July internationals.