Adrian Heskin is set for a spell on the sidelines after suffering a broken arm in a fall at Aintree on Saturday.
The Irish jockey was partnering the Tom George-trained Rocklander in the Betway Handicap Chase when his mount fell at the eighth fence.
Heskin was subsequently stood down for the day, missing out on riding The Worlds End, who finished fourth in the Ryanair Stayers Hurdle, and Saint Are, who was brought down in the Randox Health Grand National.
Speaking on Sunday morning, George said: "He's broken a bone on his arm and he's having surgery today.
"I think they'll be pinning it, but I spoke to Adrian this morning and it doesn't look like there are any complications.
"He'll be out for a while."