Quevega is to retire from racing and begin a career as a broodmare after being beaten by shock 20-1 winner Jetson in the Ladbrokes World Series Hurdle at Punchestown.
Fresh from landing the OLBG Mares' Hurdle at the Cheltenham Festival for the sixth successive year, the Willie Mullins-trained Quevega was the 9-10 favourite to secure a fifth victory on the bounce in this three-mile Grade One contest.
She travelled with her usual zest for much of the journey, but Ruby Walsh was hard at work from the home turn.
Jetson, up with the pace from outset, had already stolen a march on his rivals at the top of the straight and while Quevega did her best to reel him in after the final flight, Jessica Harrington's runner had enough in reserve to score by a length and a quarter in the hands of an inspired Davy Russell, who rode a treble on the day.
At Fishers Cross was third as the 10-year-old Quevega suffered her first defeat since 2009, and the curtain now looks set to come down on her record-breaking career.
Mullins told At The Races: "I've just spoken to the owner, I think we are going to start discussing her next career as a broodmare.
"It's not too late to cover her. Her racing career is finished now
"We didn't get a lot of luck in running, let's leave it at that.
"You'll never replace the likes of her, we try to buy good mares all the time but she'll leave a fair gap in our yard.
"I'll be sorry to see her go, but she finishes in one piece and is sound.
"She's pulled up sound, she's had a tremendous career and I'll be sorry to see her go."
He added: "She's a special mare and it would be hard to repeat what she's done.
"We'll always be trying to buy one like her but you can't replace her."
Although a consistent handicapper over staying trips, Jetson appeared to have his work cut out at this level.
In what proved a tactical affair, Knockara Beau cut out much of the running before Jetson took it up in the back straight.
The closing pack swiftly bunched up, with Quevega one of those tight for room on the inside rail, and Jetson made the most of his advantage as he took a few lengths out of the field at the top of the straight.
It proved decisive as his opponents were never able to bridge the gap and he was ridden out to secure a shock victory.
Russell said: "Jessica had him in great order and I got a great spin off him.
"To be fair, Paddy Kennedy (jockey) said the last two days he's been in the form of his life. Kate Harrington told me he'd run a blinder, so they instilled plenty of confidence in me.
"We didn't think he'd be good enough to beat the mare, but we thought he'd run well. All credit to the team."
Harrington said: "That was absolutely fantastic and a bit of a surprise.
"We ran him in this as there was no other race to run him in here. He'd have been at the top of all the handicaps.
"He comes to himself in the spring every year and he was in great form.
"I said to Davy that he stays well and he's tough, so he made use of him.
"He never missed a beat and he loves that ground.
"We did send him over fences for a while and he won a chase at Downpatrick, but he hated jumping fences.
"I thought he might run into a place as he's a fresh horse, even though he's been to Cheltenham and Aintree.
"He loves this time of year and he loves it round here.
"I didn't think in my wildest dreams he'd win, but he's run out of his skin.
"My late husband John did say 'this is the only race he can go for here, so we might as well go for it'.
"That was only Davy's second ride for me and his first winner - I think I'd better employ him a bit more now!"