Lord Gyllene, winner of the 1997 Martell Grand National, has met with a setback and is not certain to be ready in time for this year's race.
The Stan Clarke-owned 12-year-old, who has run only twice since his 25-length Aintree victory, had recovered from the pelvic injury that has kept him out of action since last February and was due to return over hurdles at Exeter on Tuesday.
However, his trainer Steve Brookshaw today said: "He's pulled a hamstring in his backside. It's nothing serious but it means he'll have to have a week's quiet.
"Tony Dobbin came down to school him yesterday and he wasn't right in the afternoon so the vet had a look at him and found the problem."
Connections now face a race against time to prepare Lord Gyllene for the Grand National on April 8th.
"The owner and I don't want to go to Aintree without getting a run into him beforehand," Brookshaw added.
