Ross Byrne held his nerve to slot a last-gasp drop goal as Leinster moved to within touching distance of the Guinness PRO12 play-offs with an 20-18 win over the Ospreys at the Liberty Stadium.
On his 200th appearance for the Ospreys Dan Biggar could have won it with the final kick of the game after a late Leinster infringement, but he pushed his penalty attempt wide as Leinster held on.
Justin Tipuric’s try looked set to give the Welsh side the perfect response to their European disappointment but Byrne stepped up with a minute to go to knock over the crucial drop goal to win it.
The Ospreys had led earlier thanks to a Sam Davies try, and even after Leinster struck back thanks to scores from Sean Cronin and Dan Leavy, Tipuric responded to give the Ospreys the lead heading into the final seconds.
However they could not hold on, and instead Leinster stretch their lead at the top of the table with the Ospreys now looking over their shoulder in the race for a top four spot.
In just the third minute Leinster were penalised at scrum-time just inside the Leinster half, but Biggar’s shot bounced off the post, allowing Leinster to clear their lines.
However it wasn’t long before a clinical Ospreys lineout and some smooth hands put Sam Davies over in the corner, with Biggar unable to convert on his 200th appearance for the region.
After a great high ball from Davies, Leinster infringed at the breakdown allowing Biggar to go for goal – making no mistake this time.
Trailing 8-0, Leinster finally finally built some phases in the Ospreys half on 16 minutes and however Dan Baker, who was outstanding in the first half, turned the ball over and allowed the home side to clear their lines.
Eventually Leinster’s pressure paid off, their backline put everything in place for hooker Sean Cronin to make an excellent break from 22 metres out, stepping his way past Biggar to the line. The conversion from Isa Nacewa was good, putting Leinster just a point behind.
After a kicking battle Leinster almost went in again, Jamison Gibson-Park just denied after Fergus McFadden’s break and clever interplay with Devin Toner.
The visitors did take the lead for the first time five minutes before half-time however, Nacewa knocking over a penalty only for Biggar to hit back with the final kick of the half to give the Ospreys an 11-10 lead at the break.
Leinster burst out of the blocks in the second half, with replacement Dan Leavy, on for Jack Conan, putting them back in front.
It came after some pressure in the Ospreys 22, with Leavy proving unstoppable from close range with a pick and drive after Robbie Henshaw and Cronin had put them into position to score.
The Ospreys needed a response with their hopes of a home semi-final hanging in the balance, but they did just that as Justin Tipuric crossed on the hour.
Like Leavy, it came from close range, with Tipuric picking and driving over and Davies slotting the conversion in the absence of Biggar who was getting patched up.
Leinster could have gone back in front with just over ten minutes to go when Leavy forced a penalty from a turnover but Nacewa’s effort drifted wide.
There was still time for plenty more excitement though, with Byrne putting Leinster back in front with a fine drop goal from 35 metres out.
Still Ospreys came and they looked to have done enough to win it, but Biggar pushed his penalty attempt to the right.
They will now face a must-win clash against Cardiff Blues at Judgement Day next weekend as they look to end a run of three straight losses.
The Guinness PRO12 Final takes place on May 27 at Aviva Stadium, Dublin.
Fans can guarantee their place by booking their tickets via www.ticketmaster.ie
Further information: www.pro12rugby.com/final