Rhys Priestland has been at the Llanelli region since the age of 18
Shane Horgan's late try denied the Scarlets top spot in the Magners League as Leinster completed a superb comeback to secure a draw at Parc y Scarlets.
Rhys Priestland passed 500 points for the Welsh region with four penalties but Jonathan Sexton's poor kicking also cost Leinster victory in Llanelli.
The Irish fly-half missed two penalties and two conversions after Eoin O'Malley and Fergus McFadden had touched down.
Sexton then crucially dropped the ball when attempting a last-gasp drop-goal.
He had dropped into the pocket to set himself to give the Irish visitors an unlikely win but Sexton's disappointing night continued as the ball slipped out of hands as referee Nigel Owens blew the final whistle.
A Friday night victory for the 2009 European champions would have been cruel on their Welsh hosts who had led by 12 points with 20 minutes remaining before Leinster's fight-back.
The Scarlets, unbeaten only once at home this season, were left to rue poor defending at key times but Nigel Davies' men did move level on points with league leaders Munster, behind them on games won, thanks to their two points for the draw.
Although it felt like two points dropped for the Scarlets coach who had eyes on top spot when Gareth Maule finished off a stunning passing move to put the hosts 17-5 in the lead.
The Scarlets could have opened their try account with a little over a minute on the clock when Morgan Stoddard dashed towards the try-line.
Scarlets and Leinster players exchange blows in the first-half
But as the Scarlets wing slid in to touch the ball down, the outstretched arm of Leinster wing Horgan got to the ball at the last second to prevent and almost certain Scarlets score.
Priestland, though, did open the Scarlets account with a penalty before Leinster hit back with a well-worked try.
Jonathan Sexton's cross-field kick was flicked back inside by Horgan who showed his ability at both ends of the field to set up Eoin O'Malley as the Leinster centre cantered over from inside the 22-yard line for his first career try.
Academy graduate Priestland passed his 500-point milestone with his second penalty as he made Leinster pay for their ill-discipline.
Priestland's third successful kick came after the simmering undercurrent at Parc y Scarlets boiled over just before half-time after an unsavoury brawl sparked by Sean O'Brien's late and high challenge on Dan Newton.
Sexton added a penalty miss to his failed conversion attempt as the Irish international was suffering an off-day.
Leinster's bad day deteriorated when last season's Grand Final runners-up were reduced to 14 men for 10 minutes when Rhys Ruddock was sin-binned for an illegal shoulder charge.
Priestland landed a fourth penalty before Maule scored his second try in successive games after a free-flowing Scarlets move.
A quick pass from Tavis Knoyle went through a host of off-loads including two cute flicks from Stephen Jones and Regan King before Stoddard set-up Maule to sprint in from 10 yards in the corner.
But once Leinster returned to full strength, they showed their trademark character and never-say-die mentality as McFadden sprinted on to Eoin Reddan's pass before skipping past Joe Ajuwa for a try.
That gave Leinster hope and confidence and returning Ajuwa, playing his first game of the season after injury, was again found wanting on the left wing as Horgan was set free by Sexton to score in the corner.
O'Brien's rampaging 50-yard run gave the visitors field position before Gordon D'Arcy and Sexton combined to send Horgan, a British and Irish Lion, over for the 85th minute score.
And if Sexton's hands were a little safer he would have snatched victory from the jaws of defeat for Leinster.
Scarlets replacement Ben Morgan knocked on under no pressure to give Leinster put-in at a scrum in front of the posts But Sexton downed Reddan's pass - and Leinster's hopes of moving into third place went with it.
To add to the Scarlets woes, their tighthead prop Phil Edwards and his replacement Deacon Manu were forced off with injury - Edwards with a suspected broken elbow.
Scarlets: Dan Newton; Morgan Stoddart, Gareth Maule, Regan King, Joe Ajuwa; Rhys Priestland, Tavis Knoyle; Phil John, Ken Owens, Peter Edwards, Damian Welch, Dominic Day, Josh Turnbull, Johnathan Edwards, David Lyons (capt). Replacements: Deacon Manu for Peter Edwards (30), Rob McCusker for Johnathan Edwards (53), Matthew Rees for Ken Owens (56), Stephen Jones for Dan Newton (56), Martin Roberts for Tavis Knoyle (66), Ben Morgan for David Lyons (66), Scott Williams for Regan King (67), Rhodri Jones for Phil John, Phil John for Deacon Manu (80)
Leinster: Isa Nacewa; Shane Horgan, Eoin O'Malley, Gordon D'Arcy, Fergus McFadden; Jonathan Sexton, Eoin Reddan; Heinke van der Merwe, Richardt Strauss, Mike Ross, Leo Cullen (capt), Devin Toner, Rhys Ruddock, Dominic Ryan, Sean O'Brien. Replacements: Nathan Hines for Leo Cullen (53), Shane Jennings for Dominic Ryan (53), Clint Newland for Mike Ross (66).Not used: Tom Sexton, Jack McGrath, Paul O'Donohue, Shaun Berne, Dave Kearney.
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