“If he’s back, and he appears to be as good as he has ever been, he is the one they all have run to beat,” Smullen told At The Races.
“It’s a very competitive race as you’d expect for a King George and Nathaniel was very impressive last time (in the Coral-Eclipse).
“It’s very open, but if you were to pick one and you had a choice St Nicholas Abbey seems to be in tremendous form and the stable is flying at the moment.”
Ryan Moore, who rides Hardwicke Stakes winner Sea Moon for Michael Stoute, also gives St Nicholas Abbey the utmost respect.
“It’s a race with plenty of strength in depth,” said Moore.
“This year you’ve got the Melbourne Cup winner, the Arc winner, Japanese Derby winner, St Nicholas Abbey, Nathaniel – it’s a very strong race.
“St Nicholas Abbey has been very good this year so far. People were quick to write him off, but he’s won four Group Ones and has shown the last couple of years what a high-class horse he is.
“Sea Moon was impressive at Ascot, but he’s got to step up a bit more to trouble the favourites here.
“He’s in good shape and he’s got scope for a bit more improvement hopefully.
“The Ascot race was run at a sound gallop. There was one hard-luck story. The other horse (Dunaden) may have been unlucky and we will find out at the weekend.”
Last year’s winner Nathaniel heads a field of 10 for the Betfair-sponsored Group One that lives up to its midsummer highlight billing, with seven of the field already winners at the highest level.
St Nicholas Abbey will be joined by stablemate Robin Hood who is likely to adopt pacemaking duties.
Michael Stoute is aiming to become the winning-most trainer in the history of the race with Sea Moon, who won the Hardwicke Stakes at Royal Ascot en-route, just like his last winner Harbinger.
Melbourne Cup hero Dunaden, judged by many to be unlucky in the Hardwicke, tackles Sea Moon again.
Danedream, last year’s surprise Prix de l’Arc de Triomphe winner, represents Germany while Deep Brillante has travelled over from Japan.
Tom Dascombe’s Brown Panther, part-owned by former England striker Michael Owen, runs, as does Ladbrokes St Leger winner Masked Marvel, a strong second-string to Gosden’s bow.
Alain de Royer-Dupre’s Reliable Man, winner of the French Derby twelve months ago, completes the field.
Meanwhile, Carlton House, second to the recently-retired So You Think at Royal Ascot, drops down in trip for the Transformers & Rectifiers Summer Mile Stakes tomorrow.
According to official ratings he will have most to fear from in-form John Gosden’s Questioning, winner of the Earl of Sefton Stakes at Newmarket in April.
Andrew Balding’s Tulius is unbeaten this year since joining the Kingsclere handler and looks to be still improving.
Pastoral Player steps up to a mile for the first time for Hughie Morrison, while Set The Trend has his first run for David O’Meara.
Red Jazz might find things a bit easier than he did against Frankel last time.
Fanunalter and Cai Shen complete the eight-runner field.