Trainer Peter Schiergen has nominated Camelot and Orfevre as the main dangers to German filly Danedream completing back-to-back wins in the Prix de l'Arc de Triomphe at Longchamp on Sunday.

The size of the task confronting the four-year-old German star is that none of the great champions who have returned for a second tilt at winning Europe's most prestigious race have succeeded since Irish colt Alleged in 1977/78.

Schiergen is confident, however, that Danedream has as great a chance as any of the previous winners even though she will confront a field which is stronger than last year.

"She is better than she was last year, well I hope so!" Schiergen said.

"She is in great shape. She is one year older but with more quality."

"The Derby winner (Camelot) and the Japanese horse Orfevre are the two that I worry about."

Camelot had looked to be an unlikely runner following his failure to land the Triple Crown when second to Enke in the St Leger a fortnight ago.

But trainer Aidan O'Brien reignited interest in the dual Derby and English 2000 Guineas winner when he said he was giving serious consideration to running him in the Arc.

The other option is the Champion Stakes at Ascot on October 20 but but he would have to take on Frankel in that race.

O'Brien will make a decision on Tuesday or Wednesday whether to run with a jockey needed because Joseph O'Brien cannot ride at the weight.

Orfevre, Japanese Horse of the Year in 2011, is seen as Japan's best chance to end its 33-year search for an Arc winner.

His victory in the Arc trial, the Prix Foy, a fortnight ago at Longchamp served to promote him to joint favourite with Danedream.

His trainer Yasutoshi Ikee has no qualms about his chances and that he will have come on significantly for that race plus he will have the advantage of being ridden by Belgian-born two-time Arc winning rider Christophe Soumillon.

"It (Prix Foy) was his first experience of running in Europe. His fitness is improving and he was only 75 per cent last time.

"Christophe Soumillon said it was a perfect trial.

"The pace must be faster than the Foy. He settled well in the Prix Foy so it should not be a problem.

"We are concerned about the crowd. On Tokyo Derby day the crowds are bigger and we coped with it okay. He had a hood on then, but no earplugs, just like at Longchamp (last time)."