One-time Melbourne Cup favourite Puissance De Lune may have run his last race.

The six-year-old was found to be lame after beating just two runners to the line in Saturday's Cox Plate won by Shamus Award and was ruled out of the Cup on Tuesday week.

He will undergo a thorough veterinary examination on Monday to determine the extent of the injury after which his owner Gerry Ryan and trainer Darren Weir will discuss his racing future.

The striking grey French import has finished second in two Group One races this spring but a win at the highest level would boost his future stud value.

"We will be looking after the horse's best interests first," Weir said.

Ryan won the 2010 Melbourne Cup with another French horse, Americain, who stood his first southern hemisphere season at Swettenham Stud this year.

Puissance De Lune was put up as the 2013 Melbourne Cup favourite a few days after last year's race when he won the Queen Elizabeth Stakes, the same event won by Makybe Diva before she went on to win three Cups.

The spring is also over for It's A Dundeel, who finished eighth as the Cox Plate favourite.

He has been booked on a plane home to New Zealand on Thursday.

The four-year-old missed his lead-up to the Cox Plate due to a foot abscess and had not raced for five weeks before he went to Moonee Valley.

Although he had to work hard wide in the Cox Plate, It's A Dundeel's jockey James McDonald said there were no excuses for his failure.

The winner of five Group One races, It's A Dundeel will be aimed at the Sydney autumn carnival in what will be his final preparation before he goes to Arrowfield Stud.