Charlie Boy has been ruled out of the Magic Millions Guineas with a hamstring injury which trainer Gerald Ryan says is likely to also ruin autumn plans.

The colt was lame when he walked out of his box on Friday morning, not long after Ryan and his owners Triple Crown announced the retirement of Group Two winning mare Flying Snitzel.

Charlie Boy was one of the leading chances for Saturday's $1 million Guineas (1400m) with his absence giving last-start Randwick winner Estonian Princess a start.

"He walked out of his box lame this morning," Ryan said.

"Previous experience tells me it is something that takes two to three months so that pretty much wipes him out of the autumn.

"It's just one of those things. He has probably over-reached and damaged it."

Flying Snitzel's retirement was prompted by a tendon injury suffered in a paddock accident.

Her finest moment came last autumn when she beat Norzita in the Group Two Kewney Stakes (1400m) at Flemington.

"Beating Norzita in the Kewney was definitely the highlight," Ryan said.

"And if she had had things go right in a few other races her record would have been even better.

"She will make a great broodmare.

"She is a lovely big mare with the potential to produce a really nice big foal."

Michael Rodd, who was to ride Charlie Boy in the Guineas, will take the mount on the Scott Asprey-trained Estonian Princess.