Jonjo O'Neill accepts it will be "a tall order" for AP McCoy to end his career with a fairytale win at Aintree.
McCoy will ride the O'Neill-trained Shutthefrontdoor in the Grand National on 11 April, indicating he will retire if he triumphs on the 8/1 favourite.
"I think AP will probably ride him and the public will all be backing him looking for that fairytale story," said O'Neill.
"We would all love it to happen, but it is a tall order."
The Jackdaws Castle trainer says his biggest challenge is to ensure last season's Irish Grand National winner gets to the Merseyside spectacular in one piece.
O'Neill reports Shutthefrontdoor in good order, having got over the setback that has kept him off the track since winning at Carlisle in November.
"I would like to have got a run into him but he had an abscess around in his sinuses back in January and February which took a while to clear up," he said.
"I would have liked to run him at Cheltenham but I decided not to as he was not as well as he is now, and I didn't want him having a hard race, which it is easy to do at Cheltenham.
"He has schooled well and is spot-on for the race. He goes there fresh and well.
"The only pressure I have on me is making sure he (Shutthefrontdoor) gets there safe and sound."
McCoy's only Grand National success to date was on the O'Neill-trained Don't Push It in 2010.