Apple's Jade secured back-to-back victories in the Christmas Hurdle in convincing fashion at Leopardstown.
Former champion hurdler Faugheen was trailing the winner by four lengths before falling at the second last.
The 8-13 favourite, ridden by Jack Kennedy and trained by Gordon Elliott, led from the early stages.
There was some relief for Willie Mullins, who holds 12 Irish champion trainer titles, as Kemboy romped to victory in the Savills Chase.
Ridden by Ruby Walsh, Faugheen sought to narrow the gap on the six-year-old mare as they closed in on the second last, however the former champion hurdler took off too soon and crashed to the ground.
After initial concern the horse rose and was walked back in by Walsh.
Last month Faugheen fell to a shock defeat at Punchestown having gone into the Morgiana Hurdle as heavy favourite only to be defeated by stablemate Sharjah.
Faugheen 'no spent force' - Analysis
Cornelius Lysaght, BBC horse racing correspondent
Life around Faugheen is full of twists and turns. 'The Machine' has hit the heights - notably at two Cheltenham and three Punchestown Festivals - plus reached an infamous low, when he pulled up in a Leopardstown race 12 months ago tomorrow, but never before has he hit the deck.
Though the winner Apple's Jade is a star turn, Faugheen held every chance when taking off too early at the second last and coming down. He's no spent force. On a day of mixed fortunes for his trainer Willie Mullins, stablemate Kemboy impressed as a young horse on the up in the big chase.
Despite her rival's fall, the story of the day was the dominance of Apple's Jade who finished strongly and far ahead of the chasing pack, with Early Doors eventually coming in to claim second.
"I had to make the running again on her, but it didn't matter. [She] jumped great, travelled away, jumped the second last and she changed gears and was away from the back of it and galloped all the way to the line. She was very good," said jockey Kennedy.
"I could see on the big screen I was fairly well clear of what was in behind me. She's unreal, she is a pleasure to be riding.
"She was in good form this time last year and then lost her way, so hopefully she can keep continuing this way anyway."