A late try from Shane Horgan denied the Scarlets top spot in the Magners League as Leinster scraped a 17-17 draw at Parc y Scarlets on Friday.
The Welsh looked certain to seal victory after opening up a 17-5 lead but in the last nine minutes tries from Fergus McFadden and Horgan earned the Irishmen a share of the spoils.
Rhys Priestland won the battle of the kickers putting over four out of five penalties with Jonathan Sexton missing ten points-worth of kicks before slotting over the final conversion which levelled the match.
Right at the end it looked as if Sexton would have a chance at a drop-goal to win the match, but he knocked the ball on.
The match went ahead as Parc y Scarlets has undersoil heating which was able to offset the freezing conditions.
The Scarlets welcomed back Matthew Rees, Stephen Jones and Deacon Manu from the autumn internationals and the trio were used as second-half replacements.
Fellow internationals George North (bruised shoulder) and Sean Lamont (bruised hip) were rested. Leinster included Ireland trio Sexton, Gordon D'Arcy and Eoin Reddan.
Despite the rainy conditions the Scarlets thought they had scored a try after only 65 seconds when Morgan Stoddart had followed up a kick ahead, but on the intervention of the TV match official the score was disallowed due to Horgan getting to the ball before the home wing.
But the Scarlets did go into a fourth minute lead when Priestland put over his first penalty from a line-out infringement.
Leinster did not have much territorial advantage but they made the most of a Sexton cross kick which Horgan passed back for centre Eoin O'Malley to race over for the only try of the half.
Either side of a flare-up following a high tackle on Dan Newton by Sean O'Brien, which saw referee Nigel Owens give both teams a serious talking to, Priestland put two penalties over on 26 and 35 minutes to give the Scarlets a 9-5 half-time lead.
The Scarlets looked in control at the start of the second half with Sexton missing two penalties and Rhys Ruddock, son of former Wales coach Mike, getting sin-binned for dangerous play at a ruck.
With the extra man centre Gareth Maule went over in the left corner for his side' only try which looked to have wrapped the match up for the Scarlets.
But after Priestland missed a penalty from halfway Leinster launched a concerted comeback with McFadden squeezing over in the right corner and Horgan following him over only five minutes later.
The Scarlets' frustrations at their failure to secure the win was compounded when they suffered serious arm injuries to props Manu and Peter Edwards.
Pen: Priestland 4
Tries: O'Malley, McFadden, Horgan
Scarlets: 15 Dan Newton, 14 Morgan Stoddart, 13 Gareth Maule, 12 Regan King, 11 Joe Ajuwa, 10 Rhys Priestland, 9 Tavis Knoyle, 8 David Lyons, 7 Johnathan Edwards, 6 Josh Turnbull, 5 Dominic Day, 4 Damian Welch, 3 Peter Edwards, 2 Ken Owens, 1 Phil John.
Replacements: 16 Matthew Rees, 17 Rhodri Jones, 18 Deacon Manu, 19 Rob McCusker, 20 Ben Morgan, 21 Martin Roberts, 22 Stephen Jones, 23 Scott Williams.
Leinster: 15 Isa Nacewa, 14 Shane Horgan, 13 Eoin O'Malley, 12 Gordon D'Arcy, 11 Fergus McFadden, 10 Jonathan Sexton, 9 Eoin Reddan, 8 Sean O'Brien, 7 Dominic Ryan, 6 Rhys Ruddock, 5 Devin Toner, 4 Leo Cullen (c), 3 Mike Ross, 2 Richardt Strauss, 1 Heinke van der Merwe.
Replacements: 16 Tom Sexton, 17 Jack McGrath, 18 Clint Newland, 19 Nathan Hines, 20 Shane Jennings, 21 Paul O'Donohoe, 22 Shaun Berne, 23 Dave Kearney.
Referee: Nigel Owens