The seven-year-old, who has won his nine starts over fences, made the step up to two-and-a-half miles by winning the Melling Chase by four-and-a-half lengths at Aintree on Friday.
Geraghty now believes that he can make the step up to three miles for the Boxing Day King George.
He told Racing UK: "The King George wouldn't be as strong a race as [the Melling].
"He's got youth on his side. If he didn't go for the King George this Christmas he could go for it the following year."
Geraghty's ride in the Grand National later today is current 22/1 shot Roberto Goldback.