Andy Stewart is still perplexed by Aiteen Thirtythree's moderate performance in the Hennessy Gold Cup at Newbury last month.
The Paul Nicholls-trained seven-year-old was sent off favourite for the prestigious handicap following an excellent second at Kempton, but weakened quickly to finish only 11th of the 14 finishers.
Stewart hopes the gelding can make up into a Grand National contender, but is unsure where he will turn up next.
"He's absolutely fine but we still haven't got to the bottom of what happened," said Stewart.
"The options are open for him and the long-term plan if we can get him there is the Grand National.
"Ruby can't understand what happened at Newbury. He thinks he's a National horse so the fact he weakened quickly over three and a quarter miles is a bit confusing.
"We've just put a line through it and we'll see if we can get him back on track."