The racing future of trans-Tasman Group One winner King Mufhasa is in doubt after the gelding bled during Sunday's Champions Mile in Hong Kong.

Trainer Bruce Wallace said King Mufhasa's trachea had filled with blood during the race and he was struggling to breathe as he came off the track at Sha Tin.

Wallace said he never gone into a Group One race more confident than he did on Sunday.

"When we got to the races he looked like a stallion, just fantastic, and Michael (Rodd) said he felt tremendous in his preliminary," Wallace told reporters in Hong Kong.

Wallace said the 10-time Group One winner had not pulled up lame as stated during the broadcast of the Sha Tin meeting, but he is nevertheless concerned for the gelding's welfare.

He said the cause of the bleeding would be investigated with a view to making a decision on the future.

King Mufhasa appeared to travel well outside the lead in Sunday's race, but gave ground quickly from the 400m mark and was virtually pulled up.

"What happens next won't be up to me, he'll stay her for a month and we'll assess the situation during that time," Wallace said.

Wallace took over King Mufhasa's training from Stephen McKee earlier this year with Sunday's run his fifth for the trainer.

As well as including most of New Zealand's best middle-distance races among his 20 wins, King Mufhasa won the Toorak Handicap and Futurity Stakes, both at Group One level, in Melbourne.

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