The Lady Blyth-owned gelding, priced at 18/1, gained a fifth win over hurdles when dead-heating with Epatante last November in the race.
It was very soft ground last year, but Morrison has allayed any ground concerns for the 10-year-old and insists the gelding will go to post in the North East.
Not So Sleepy followed up that run when fifth of five in the Christmas Hurdle with Epatante taking the honours on the soft at Kempton. He was subsequently sixth in the Champion Hurdle, beaten nine lengths by the classy Honeysuckle.
But the three-time Ascot winner showed his versatility on the Flat when again placed in the Cesarewitch on his latest outing last month. The 40/1 chance finished four-and-a-quarter lengths behind Run For Oscar on good ground at Newmarket .
He is one of six entries for the Betfair-sponsored Grade One and is likely to come up against Nicky Henderson pair Epatante and Champion Hurdle favourite Constitution Hill.
Morrison said: "I think we will run regardless. He is an intended runner, we have every intention of running, unless the owners tell me not to run him.
"I don't think the ground will be too bad. It won't be any quicker than good to soft. He has run well on good ground on the jumps, which is soft ground on the Flat, basically.
"We are hoping for a bit of rain in the week and maybe a bit of rain on the morning - that would suit him. What he loves is slopping through it. We'd love it to be wet in the afternoon, so it comes loose and sloppy rather than sticky.
"Whoever turns up, turns up. If Nicky Henderson wants to send his string, that's fine by me."
Not So Sleepy has been unpredictable in the past, famously unseating his rider at the first in the 2020 edition of the race and carrying out Silver Streak.
H Morrison added: "He has been his usual, sometimes naughty self, but we have got enough grey hairs from him already, so we are trying to enjoy it.
"He has been a great horse for us, and we will miss him when he retires."
Only six horses were confirmed at the five-day stage with Pied Piper, Tommy's Oscar and Voix Du Reve the others declared.