The Aidan O’Brien-trained four-year-old, who also won the St Leger last season, was badly hampered by the eventual winner of the British Champions Long Distance Cup, Forgotten Rules, and the result of the incident is injuries to both his front legs.
O’Brien feels the setback may be enough to force the son of Montjeu into retirement.
The Ballydoyle handler said: “It was an unfortunate incident and the unfortunate part was the horse came out of it the wrong side.
“He has two very bad injuries to both his front legs and there’s a chance he might never race again.
“It’s very disappointing.”
Meanwhile connections of Tullius may resist the temptation of sending him overseas this winter and save him for a return to action in the spring.
The six-year-old performed admirably on Champions Day at Ascot on Saturday, finishing fourth in the Queen Elizabeth II Stakes as French raider Charm Spirit claimed top honours.
The bet365 Mile at Sandown in April and the Lockinge Stakes at Newbury in May, in which Tullius was first and second this year, would be the targets if owners Kennet Valley Thoroughbreds and trainer Andrew Balding decide not to take him to Hong Kong and Dubai.
“He ran an absolute cracker. Probably the draw didn’t quite work for him. Jimmy Fortune said if he’d been on the rail it would have helped him get in the race better,” said Kennet Valley racing manager Sam Hoskins.
“He perhaps hit the front too soon. He wouldn’t have beaten Charm Spirit, but he just might have been third.
“We’re so proud of him and he’s done really well.
“It’s a debate now whether he goes abroad or not to Hong Kong and Dubai. Probably what we’ll do is to give him a few months off and go for the bet365 Mile at Sandown and then try to go for the Lockinge again.
“He likes soft ground ideally though he did come second in the Lockinge on fast ground.
“We’re thinking about it. It’s a nice problem to have.”