The French-trained colt finished third to Luxembourg in a strong renewal of the Irish Champion Stakes at Leopardstown on Saturday.
Last seen winning the Eclipse at Sandown in July, Christophe Soumillon's mount did not have much luck in running during the 10-furlong contest.
Vadeni, who had been a general 10-1 for the Arc on October 2, had to weave his way through the field to get within a length and a half of the winner.
Rouget was offering no excuses for the 7-4 favourite and said: "He came up the outside and then he had to go inside and he was having to do a slalom, like in skiing.
"So it was quite a good run. He was in front of Mishriff like he was last time and we can't win every race.
"I think he was a bit unlucky, but I think the result is correct with a very strong pace in front.
"I don't know what the plan is, but not the Arc for now. Maybe he goes to Ascot (Qipco British Champion Stakes on October 15) if the ground is better. Maybe."
Connections of Mishriff are considering a tilt at the Breeders' Cup Turf after he finished a gallant fourth.
The John and Thady Gosden-trained colt, who many considered to be slightly unlucky in running when beaten a neck in the Eclipse, finished three-quarters of a length behind the French challenger this time.
Jockey Colin Keane, who replaced injured James Doyle, held up Mishriff in the early stages and he stayed on well inside the last furlong, despite running on slower ground which did not appear to suit.
Thady Gosden said: "They had plenty of rain here during the week, but the drying conditions made the ground a bit tacky and holding.
"He managed to pick up on it once, but he couldn't quite do it a second time and the first three are top-class horses.
"The ground wasn't perhaps to his liking and all credit to the winner."
The Prince Faisal-owned Mishriff, who was a runaway winner of the Juddmonte International last season and who had finished six and a half lengths behind the world's top-rated horse Baaeed in defence of his York crown on his previous run, could now head to Keeneland on November 5.
Prince Faisal's racing manager, Ted Voute, said: "Post-race, John Gosden would like to consider the Breeders' Cup Turf over a mile and a half.
"Colin Keane felt the ground was drying and felt a bit dead, which he wasn't happy on. He finished well, considering.
"Prince Faisal has said that the Breeders' Cup wasn't out of the question, provided he comes out of the race well."