Even if Leinster were minus five Lions, this was not the stuff of European champions. Far from it. It was a match they should have won and looked like winning comfortably until they fell away dramatically in the final quarter.

With eight of the players who helped to win the Heineken Cup final against Leicester in May on show nothing but a victory seemed possible against a Scarlets side unfancied by all and sundry in the pre-season round of punditry.

At half-time the Scarlets were fortunate to be still hanging on to Leinster's coat tails, having conceded a soft try and then having been reduced to 13 men at one stage, with new forward recruits Richie Pugh and Rhys Thomas in the sin-bin.

But the home side trailed only 16-10 at the interval and as the second half progressed the wheels started falling off Leinster's wagon, leaving their head coach, Michael Cheika, less than enamoured with his side's inability to kill the game off.

"We put ourselves into a position to win and we didn't take the opportunity we gave ourselves. We got ill-disciplined. We had opportunities to score in each corner but our forwards got lazy. We didn't work hard enough," he said. "That's what you get if you take your foot off the pedal for 10, 15 minutes, you'll get beaten away from home. For 70 per cent of the game we played pretty good for our first outing. It was that other 30 per cent we let our guard down."

Leinster's problem, apart from missing the likes Brian O'Driscoll, Jamie Heaslip, Luke Fitzgerald, Nathan Hines and Rob Kearney, was that they were twice cut down to 14 men. The worst offender was Stan Wright, who blatantly took out David Lyons at the side of a ruck. That allowed Scarlets to gain their first decent attacking foothold in Leinster territory since new signing Sean Lamont, the Scotland wing, had breezed in for a fine try in the sixth minute.

The young centre Jonathan Davies was at the forefront of the home side's search for a second try, which came through replacement prop Phil John. Rhys Priestland missed the conversion which would have given them the lead but struck the all-important penalty goal nine minutes from time.

The Scarlets coach, Nigel Davies, was pleased with the opening win but not with his team's discipline, especially with Thomas later cited for alleged use of the head on Shane Horgan. "We are a team in transition. We had a difficult season last year. We have turned a new page and moved things forward," he said. "But it's simply not acceptable to go down to 13 men. It puts pressure on the rest of the team and we've got to come down hard on it. The guys on the field were heroic in how we dealt with it.

"But being reduced to 13 men costs you games and I can't have that. It's a major issue. We will look at selection and look at other things as well to sort this out."

Scarlets Evans; Lamont, Higgitt (Williams, 55), Davies, M Jones (capt); Priestland, Roberts; I Thomas (Manu, 61), Owens, R Thomas (John, 61), Reed (Cooper, 71), Day, Easterby (D Jones, 58), Lyons, Pugh.

Tries Lamont, John. Con Priestland. Pens Priestland, 2.

Sin bin Pugh, 32; R Thomas, 38.

Leinster Dempsey (Keogh, 70); Horgan, McFadden (Morris, 75), Berne, Nacewa; Sexton, Keane; Healy, Fogarty, Wright, Cullen (capt), O'Kelly (Toner, 67), McLaughlin, Jennings, Keogh (O'Brien, 42).

Try Dempsey. Con Sexton. Pens Sexton, 3.

Sin bin Wright, 46; O'Brien, 68.

Referee Neil Paterson (SRU). Attendance 6,075