Pro12: Ospreys v LeinsterOspreys (11) 18Tries: Davies, Tipuric Con: Davies Pens: Biggar 2Leinster (10) 20Tries: Cronin, Leavy Cons: Nacewa 2 Pen: Nacewa Drop-goal: Byrne
Dan Biggar missed a 40-metre penalty with the last kick of the game as Ospreys lost to a much-changed Leinster at Liberty Stadium.
Ross Byrne’s 79th-minute drop goal had edged the visitors ahead after Ospreys led 18-17 from the 62nd-minute.
Tries by Sam Davies and Justin Tipuric had helped give the home team a slender advantage.
Sean Cronin and Dan Leavy crossed for Leinster, who took a huge step towards a home draw in the Pro12 play-offs.
The win extends Leinster’s lead at the top of the table to seven points before second-placed Munster’s match with Glasgow on Saturday evening.
Showing eight changes in personnel from their European Champions Cup win over Wasps, Leinster were cool under pressure and responded brilliantly after a sluggish start.
Ospreys’ place in the top four will come under threat if Scarlets beat Treviso on Saturday, potentially cutting their cushion over fifth place to two points.
Biggar lined up to take the penalty after returning to the field following treatment for a cut head, and said on television he was dazed and could remember little of the final 10 minutes.
For their part, Leinster could have paid a heavy price for opting to go for the corner instead of kick for goal from a penalty when the score was 17-11 in their favour.
But replacement Byrne’s drop goal – and Biggar’s miss – meant their gamble was not ultimately punished.
Ospreys make early running
Ospreys made all the early running and were ahead within four minutes when Davies dived over wide on the right after Rhys Webb, Josh Matavesi and Olly Cracknell made good ground up the middle.
Biggar missed the conversion after earlier hitting a post with a long-range penalty attempt, but was on target to give the home side an 8-0 lead after nine minutes.
Leinster were possibly disrupted by their changes in personnel from the 32-17 European Champions’ Cup win over Wasps, but struck back in style in the 23rd minute.
Cronin swerves past Biggar
Exploiting some uncertain defending in the wide channels, Zane Kirchner set Cronin free and the Ireland international hooker celebrated his first start since January with a swerve past Biggar to run-in from 30 metres.
Full-back Isa Necawa added the extras and a penalty before Bigger struck on the stroke of half time to restore Ospreys’ lead.
Cronin was in on the act again early in the second half, bursting up to the Ospreys tryline to set up the attack from which half-time replacement Leavy twisted and rolled over for the second Leinster try.
Ospreys hit back after Davies’ spiralling touch finder set up a position from which Rhys Webb sniped to within inches of the line and Tipuric touched down.
Davies’ conversion edged the Ospreys back ahead.
There was no hint at that stage of the drama that was to follow in the dying minutes.
Leo Cullen, Leinster head coach: “I did think he (Biggar) would put the kick over. But it looked like a bit of a tired kick and it had been a draining game and it looked like the game had taken its toll.
“When he stepped up to it I thought there was a fair chance he was going to kick it.”
Steve Tandy, Ospreys head coach: “It’s a pretty devastated changing room in the fact that we’re coming off the wrong end of some scoreboards, but we’ve just got to dust ourselves off and get back on the horse.
“We’ve got a big match now on Judgement Day (v Cardiff Blues) and the only crumb of comfort in it all is we’re still in control of getting into the top four, but it’s a bitterly disappointing result.”
Remaining Pro12 matches:
Ospreys: 15 April: Cardiff Blues (Principality Stadium); 29 April: Ulster (H), 6 May: Scarlets (A).
Leinster: 15 April: Connacht (A), 28 April: Glasgow (H), 6 May: Ulster (A)
Ospreys: Sam Davies; Keelan Giles, Kieron Fonotia, Josh Matavesi, Dan Evans; Dan Biggar, Rhys Webb (capt); Nicky Smith, Scott Baldwin, Brian Mujati, Lloyd Ashley, Rory Thornton, Olly Cracknell, Justin Tipuric, Dan Baker.
Replacements: Scott Otten, Paul James, Ma’afu Fia, Bradley Davies, Tyler Ardron, Sam Underhill, Tom Habberfield, Jonathan Spratt.
Leinster: Isa Nacewa (capt); Rory O’Loughlin, Zane Kirchner, Robbie Henshaw, Fergus McFadden; Joey Carbery, Jamison Gibson-Park; Jack McGrath, Sean Cronin, Tadhg Furlong, Devin Toner, Mick Kearney, Rhys Ruddock, Josh van der Flier, Jack Conan.
Replacements: James Tracy, Peter Dooley, Mike Ross, Ian Nagle, Dan Leavy, Nick McCarthy, Ross Byrne, Dave Kearney.
Referee: John Lacey (IRFU)
Assistant referees: David Wilkinson (IRFU), Rob Price (WRU)
TMO: Neil Paterson (SRU).