Her decision means Barry Geraghty will not be faced with the dilemma of having to choose between the 10-year-old and brilliant John Durkan Punchestown winner, Kicking King.
Moscow Flyer produced a tremendous performance at Sandown on Saturday to beat Azertyuiop and Well Chief in a thrilling Tingle Creek Chase.
Harrington said: “We made the decision this morning that it wouldn’t be right to take him back to England again just three weeks after Sandown.
“The horse is fine, but in the context of the whole season it is the right thing to do. If he had got beaten at Sandown it would have been easier to go to Kempton.”
Moscow Flyer’s campaign will now be geared towards winning another two-mile Champion Chase at Cheltenham.
He produced a scintillating display to land the Champion Chase last year, but then crashed out of the Grade One in March, leaving Azertyuiop in for an easy success.
Harrington said that Moscow Flyer, who will now head for Leopardstown at Christmas, was likely to have a further outing on the run-up to the Festival, reasoning he went there too fresh last time.
Edward O’Grady confirmed that Back In Front will throw down the gauntlet to Rooster Booster in the Bula Hurdle at Cheltenham on Saturday. Davy Russell takes the ride.