He has suffered a recurrence of an old leg injury and is expected to be on the easy-list for between 12 and 18 months.
Bust Out, quoted at 10-1 by Cashmans for the Arkle, behind 2-1 favourite Azertyuiop, won the Irish equivalent, the Arkle Cup, at Leopardstown in January.
The seven-year-old was expected to run a big race at the foot of the Cotswolds, in an attempt to give Harrington back-to back Arkle successess. She, of course, won the race last year with Moscow Flyer, who is favourite and right on course for Cheltenham’s two mile Champion Chase.
Moscow Flyer worked on the Curragh yesterday morning and schooled over a couple of fences, delighting his big-race pilot, Barry Geraghty.
Speaking about Bust Out, Mrs Harrington said: “When he comes back he will still be a young horse!’’
Meanwhile Noel Meade’s Khetaam has a leading chance in the Ryan’s Pub Ratoath Hurdle at Fairyhouse this afternoon.
The consistent five-year-old has been going well all season and may benefit from stepping up to two and a half miles for the first time. Certainly, he appeared to be chopped for speed, over the minimum trip, at a vital stage at Navan in January when beaten into third spot behind Nil Desperandum and Fota Island. Previously, Khetaam won his maiden in a canter at Gowran Park (two and a quarter miles) and was a creditable head second to the smart Scarthy Lad at Navan. A stayer on the flat, he may well come into his own now!
Collier County and Leinster are the two to concentrate on in the James Lawless Bar and Hardware Maiden Hurdle.
The long-absent Collier County was gambled on to make a successful comeback at Navan 13 days ago, but faded badly from before the final flight when a well beaten fourth behind Supreme Developer.
Leinster is a decent horse who has been struggling on heavy ground. It found him out at Leopardstown, when fourth behind Back In Front and, on this surface, a fitter on this occasion Collier County is preferred.
Our old friend Mitchelstown pops up again in the John McCarthy Motorpoint Saab Bumper and is the one to beat. He never runs a bad race and was seen to good effect one more time when third behind the highly rated John Oliver and the promising Hit The Net at Naas last Sunday.
Bassett Tiger, who would have won at Punchestown but for falling at the last, is the choice to take the Mulhuddart Beginners Chase.
The somewhat frustrating Fota Island gets the nap to finally get off the mark over jumps in the Rockbrook Maiden Hurdle at Leopardstown tomorrow.
He was rather surprisingly beaten five lenghs by Mossy Green at Naas towards the end of January and, at the time, it looked a poor enough effort.
But Mossy Green has since shown the form in a totally different light and a refreshed Fota Island can now do the business.
The once-raced this campaign, Alexander Milenium, gets the vote to take the Stepaside Novice Chase.
He was one of the best bumper horses in the country last season but, like a lot of Mullins’ inmates, has been well below par of late.
The selection made a belated seasonal debut at Leopardstown, when thrown in at the deep end in the Grade One Arkle Cup. Alexander Milenium jumped brilliantly, until toppling over when tiring two out, in a contest won by Bust Out. He will surely come on for both the experience and the much needed outing!