A tendon strain has ruled Mourinho out of the Australian Cup.

Trainer Peter Gelagotis said the gelding has a slight strain to his left foreleg.

"His (work) rider said he didn't feel 100 per cent and that's how we found the problem," Gelagotis said.

Retirement now looms for the rising nine-year-old who has won 11 races from 42 starts and more than $1.35 million in prize money.

Gelagotis said Mourinho would need 12 months rehabilitation if he was to make it back to the racecourse.

Mourinho didn't race for almost 18 months after injuring a tendon as a four-year-old.

"These things, to do them properly, need time and we don't have the time with him anymore," Gelagotis said.

"We haven't made a decision on retirement as yet but the general consensus is put him out while he's on top of his game and then let him see his days out.

"He's done a great job for us."