Two years after the high of a Melbourne Cup win, French jockey Christophe Lemaire hit rock bottom in a tragic end to his dream of a second Cup.

Lemaire won on Dunaden in 2011 and went into Tuesday's renewal confident he could repeat the result on the Aga Khan's mare Verema.

But the horse fractured a cannon bone at the 2000m mark and could not be saved.

"It's just bad luck," Lemaire said.

"There were no signs before the race something like that would happen.

"She was on the bridle travelling well alongside the future winner, we were in a good position, but these kinds of things just happen."

While Lemaire was "very sad", Verema's strapper was inconsolable after the Cup.

"She was a good mare. I won a couple of Group races with her in France," Lemaire said.

"You come here dreaming about winning the race, not having this happen halfway round."