Depleted Ospreys dramatically secured Champions Cup qualification for next season as they notched three late tries to stun Leinster’s second string 24-19.

Leinster looked in control as two Harry Byrne tries and a Jamie Osborne score helped them lead 19-3 after 68 minutes.

But Olly Cracknell’s touchdown gave Ospreys hope before further late Owen Watkin and Josh Thomas tries.

Replacement Thomas’ 76th-minute try came as he charged down Byrne’s attempted clearance from the edge of the Leinster 22 and ran on to grasp possession after Leinster full-back Max O’Reilly had failed to gather the loose ball.

The joy of the Ospreys players told a tale as the dramatic win ended a run of three straight defeats and Glasgow’s hopes of snatching the European Champions Cup qualifying spot in Conference A.

Leinster had scored two tries in the first half during the sin-binning of Ospreys prop Ma’afu Fia but Ospreys went one better in the closing 12 minutes after Leinster replacement Andrew Smith had been yellow carded by referee Chris Busby.

For most of the contest, the narrative looked likely to be how Leinster’s supporting cast – after a slow start – had advanced their selection claims for next weekend’s Pro14 final against Munster.

Toby Booth’s side did create early chances as scrum-half Reuben Morgan-Williams failed to hold on to a Watkin pass with the line gaping and Dewi Cross’ chip over last defender Rowan Osborne bounced agonisingly into touch when a try seemed in the offing.

However, Leinster regrouped and sustained pressured forced a number of offside infringements which eventually resulted in the sin-binning of Ospreys prop Ma’afu Fia.

Leinster notched two tries when Ospreys were down to 14 men with Byrne’s first touchdown and Jamie Osborne’s score coming either side of a Luke Price penalty, with the second try a scrappy affair from the visitors’ perspective as they failed to deal with the restart.

After leading 12-3 at the break, Michael Bent’s burst set up Byrne’s second try four minutes after the restart and the scoreline remain unchanged for the next 25 minutes as Leinster seemed in total control.

However, the home scrum began to concede penalties as Ospreys’ bench made a big impact.

Smith was sin-binned after catching Dewi Cross with a high tackle in the 67th minute and the Ospreys pack piled through for Cracknell to dive in beside the posts.

Twenty-year-old replacement Thomas coolly converted and also added the extras to Watkin’s rumble for the line, following a furious chase and steal by flanker and man of the match Morgan Morris.

Victorious in Ireland on only two previous occasions since 2016, Ospreys snatched the result when Thomas followed through on his charging down of Byrne’s kick, as he got the better of O’Reilly to grasp the ball and touch down under the posts.

Ospreys flanker Morgan Morris:

“You couldn’t really write it, we’re all on a high as you could hear from the noise from the bench, the loudest you’ve heard us all year and it’s amazing.

“It’s been a bit of a theme that we started well and dominated but we haven’t got the points on the board in the last few weeks, but we somehow pulled it out in the last ten minutes. We stuck to the way we play and pulled out a big win.”

Ospreys head coach Toby Booth:

“I’m delighted because of the hard-fought nature of it, to come to the home of the champions and the nature of how we’ve gone about it is joyful for the people watching at home and rewards all our hard work.

“I’m delighted for the youngsters who’ve thrown themselves into it week in week out, represented our people and our region and it’s really great for us.

“From where we’ve come from, it’s a great stepping-stone (to secure European top-tier qualification) but we’ve got plenty of work to do.”

Leinster: Max O’Reilly; Rory O’Loughlin, Jamie Osborne, Ciaran Frawley, Dave Kearney; Harry Byrne, Rowan Osborne; Peter Dooley, Sean Cronin. Michael Bent, Ross Molony, Devin Toner, Scott Fardy (capt), Scott Penny, Josh Murphy.

Replacements: Dan Sheehan, Marcus Hanan, Thomas Clarkson, Jack Dunne, Sean O’Brien, Hugh O’Sullivan, Tim Corkery, Andrew Smith.

Ospreys: Dan Evans (capt); Dewi Cross, Owen Watkin, Keiran Williams, Cai Evans; Luke Price, Reuben Morgan-Williams; Rhys Henry, Sam Parry, Ma’afu Fia, Lloyd Ashley, Rhys Davies, Will Griffiths, Morgan Morris, Gareth Evans.

Replacements: Dewi Lake, Garyn Phillips, Tom Botha, Olly Cracknell, Sam Cross, Shaun Venter, Josh Thomas, Joe Hawkins.

Referee: Chris Busby (IRFU)

Assistant Referees: Sean Gallagher and Stuart Gaffikin (both IRFU)

TMO: Olly Hodges (IRFU)