Pastorius, winner of three Group 1 races and Germany's champion three-year-old of 2012, suffered a career-threatening injury on Monday morning.

Trainer Mario Hofer confirmed on Tuesday that his star colt fractured a cannonbone and faces six weeks in plaster.

"He was doing his first serious work since the Eclipse, where he ran below form as the ground was too firm for him," Hofer said. "He worked well, but came back slightly lame on his right fore, and as this got worse we called the vet and had him x-rayed.

"It is not a complicated break, but it means six weeks box rest with his leg in plaster. If he makes a complete recovery, we shall keep him in training as a five-year-old, but if we have any doubts at all, we shall start looking for a place for him at stud."

Plans to run again this season have been scratched and with them a shot at the Group 1 treble of Grosser Preis von Baden, Qatar Prix de l'Arc de Triomphe and Qipco Champion Stakes.

Pastorius ran fourth to Frankel in the 2012 Champion Stakes having beaten Novellist to win the Deutsches Derby earlier in the season before adding the Grosser Dallmayr-Preis - Bayerisches Zuchtrennen.

He achieved a rating of 122 in the 2012 World Thoroughbred Rankings, just 2lb shy of that gained by Germany's King George-winning heroine Danedream.

This season Pastorius added the Group 1 Prix Ganay before a fruitlesstrip to Singapore then a sixth place to Al Kazeem in the Eclipse.

Hofer said: "A decision will be made on his future when he comes out of plaster in October.

"It is obviously very disappointing as he had a major autumn campaign planned but that's now out of the question."

Pastorius, a four-year-old son of Soldier Hollow, races for Stall Antanando and has won six of 14 starts for earnings of £638,260.