Brett Doyle will keep the ride aboard top weight SenSmith's Northumberland Plate at Newcastle on Saturday.
Doyle partnered the horse when he won on his British Flat debut at Newmarket last month, but trainer Nicky Henderson had considered putting up an apprentice to ease Sentry Duty's burden.
He said: "Brett gave him a great ride at Newmarket and he will stay on board. We toyed with claiming only because 9st 10lb seemed a lot of weight, but Brett knows him and he will understand the hurly-burly of this highly-competitive race."
Sentry Duty was a six-time winner in France before switching to Henderson's care at the start of the year as a jumping prospect.
Although the five-year-old finished fourth over hurdles in March, Henderson admits his hand has been somewhat forced as he wants to preserve Sentry Duty's novice status.
"I wasn't mad keen on losing his maiden in an ordinary novice hurdle, so rather than keeping him for next season that's why we have taken up the Flat route for the time being," he explained.
"The idea had been to go for the Ascot Stakes, but I'm afraid he did it so well (at Newmarket) it took us out of the top of that, so this looks a logical alternative.
"If it does get very soft, it does inconvenience a certain number of horses, but luckily we think and hope with him that rain is not a disadvantage and he will be able to cope with it."
Len Lungo has his fingers crossed Monolith makes the cut. The Carrutherstown trainer would like another crack at the Gosforth Park feature after springing a 33-1 surprise with Mirjan in 2004.
However, Monolith needs seven horses need to come out to get a place in the £200,000 heritage handicap over two miles.
The nine-year-old, owned by the Elite Racing Club, pleased his trainer when fourth under top weight over two and a quarter miles at Pontefract on Sunday.
"The ground at Pontefract was nice and easy. A horse could let himself down with no risk," said Lungo.
"I know he was only fourth, but he's a small horse who had top weight and he was trapped on the outside."
Trainer George Moore would love the chance to win the Plate for a second successive year.
Twelve months ago, the Leyburn-based handler sent out 33-1 outsider Toldo to land the `Pitmen's Derby'.
Now he is pinning his hopes on Macorville, who needs two horses to be withdrawn to be guaranteed a run.
"He's in great order and if he gets in he's going to run," said Moore. "It would be lovely to win the race two years running."
The ground is currently on the soft side at Newcastle and Moore hopes there will be plenty of cut at the weekend.
"The softer the ground the better. He really copes well with soft ground," he added.
"We took him to Ayr on Saturday, but it was too firm so we didn't run him. We fancied him up there and thought he would run a cracker."
Full House is unlikely to take his chance in the race unless conditions at Newcastle improve. Trainer Paul Webber will monitor the weather over the next few days but will not risk the Ascot Stakes winner on rain-softened ground.