Leinster 20 Ospreys 16:Leinster produced what had looked an unlikely second half performance against Ospreys at the RDS to overturn a six-point deficit and cement their place at the top of the Magners League. The European champions now know they can ensure a home semi-final with a win against Connacht in Galway next week.
Ospreys procured a bonus point that kept them in second place but they are just one point ahead of Glasgow Warriors, four ahead of Munster, who play Connacht on Sunday, and seven adrift of Leinster.
The win looked unlikely at the break after an Isa Nacewa intercept try was cancelled out, and some, by a touch down and four kicks from four from Dan Biggar.
However, the homeside emerged with far more purpose in the second and Shaun Berne ran in a deserved try after two early line breaks and Fergus McFadden converted.
The centre then added a long range penalty to keep Ospreys at arm's length. McFadden had missed two easier kicks in the half but the manner in which he finished the third was testament to his mental fortitude.
Both sides were much changed from their last outings and there were also late alterations as scrumhalf Paul O'Donohoe came into the Leinster team and Gareth Owen replaced Lee Byrne at full-back for the Ospreys.
The visitors managed to dominate the first half in terms of possession and territory, with a decidedly flat Leinster side making only two visits to the Welsh region's 22.
Still, Leinster opened the scoring against the run of play in the 12th minute. Back rowers Filo Tiatia and Jerry Collins linked in midfield as the Ospreys rumbled into the home 22.
But, off the ensuing ruck, Biggar's looping pass was too ambitious, Nacewa plucked it out of the air and the Auckland-born winger had the pace to run over unopposed from 80 metres.
McFadden tapped over the conversion but discipline and restarts - two areas Leinster coach Michael Cheika singled out for additional work after last weekend's Heineken Cup quarter-final win - let the hosts down again.
The Ospreys attacked with vigour off the restart, and Biggar traded penalties with McFadden before the men in white bossed the remainder of the opening half.
The talented number 10 hit a monster penalty from just inside the Leinster half to close the gap to 10-6 and Shane Williams was bundled into touch in the right corner as the Ospreys continued to press out wide.
They adjusted coming up to half-time, finding more space through the middle of the Leinster defence.
Biggar, having missed an earlier drop goal, redeemed himself by waltzing through for a 31st-minute try, shrugging off Mike Ross' challenge after the Ospreys had profited from an Ian Gough lineout steal.
Full-back Owen produced a solid tackle on Nacewa to win turnover ball and an eventual penalty which Biggar dispatched through the uprights with aplomb.
Gordon D'Arcy and Jamie Heaslip tried to inject some pace into Leinster's attacks coming up to the break, but the Ospreys stood firm for a 16-10 half-time lead.
However, it was a different story after the interval as Leinster took the intensity up a notch or two and the Ospreys' effort waned, which was understandable in their third game in six days.
James Hook, the two-try hero against Ulster on Tuesday, could not exert the same influence on proceedings and Australian Berne saw more ball behind an advancing Leinster pack.
McFadden missed an early penalty chance, but Berne settled the league leaders' nerves by breaking the first line of defence, off quick lineout ball, to canter in under the posts on a diagonal run. McFadden converted for a 17-16 lead.
There was a long listless period before McFadden missed the target from a 66th-minute penalty and Berne also had a drop-goal ruled out.
But, despite ending the match on the defensive, Leinster sealed the points with five minutes to go.
Their grip on the game was tightened when Ospreys lock Gough was sin-binned for blocking Berne in midfield as he chased his own chip.
McFadden pulled out all the stops to nail his most difficult kick of the night, driving Leinster to their 14th straight league win at the RDS and putting them within touching distance of the semi-finals.