The clash between Energumene and Shishkin is off at the 2021 Cheltenham Festival, after the Willie Mullins-trained star met with a setback.
The pair were due to meet in the Sporting Life Arkle Challenge Trophy Novices' Chase on the opening day, March 16.
Mullins revealed on Friday morning that Energumene, unbeaten in three starts over fences this season, had encountered a hold-up in training.
"Unfortunately, Energumene has met with a setback and won’t be running at the Cheltenham Festival next week," he tweeted.
"It is very disappointing for all connections."
The seven-year-old's race against Shishkin, the winner of the Sky Bet Supreme Novices' Hurdle at last year's meeting, was set to be one of the most exciting match-ups this time around.
Energumene's final outing before Cheltenham came at the Dublin Racing Festival on February 6, where he came home ten lengths clear of stablemate Franco De Port.
Bookmakers have cut Shishkin's price in to as short as 8-15 for the Grade 1 contest next week.
On Friday, in another blow for ante-post punters, it emerged that Paddy Power Stayers' Hurdle joint-favourite Thyme Hill would miss the race.
Philip Hobbs' charge was being prepared for a third clash with 2019 winner Paisley Park in the feature race on day three.
