Darley colt Sessions is recovering well after undergoing surgery to remove a testicle.

Swelling in that area resulted in his scratching from last Friday night's Canterbury Classic for which he had been the pre-post favourite.

Trainer Peter Snowden said Sessions' condition was "extremely rare" and not one he had seen before during his time in racing.

It was the latest blow for the promising colt whose career has been restricted to five starts due to injury.

"His whole life has been about that sort of thing. He's been one of the unluckiest horses you could come across," Snowden said on Sydney's Sky Sports radio.

Snowden said the loss of a testicle would not impact on a potential stud career for the well bred son of Lonhro.

"There are quite a few well known stallions now in the Hunter Valley that serve with one testicle," he said.

"It's not like it can't be done, they manage quite well actually."

The winner of three of his five starts, Sessions will be given a well deserved break in the paddock for two or three weeks before Snowden puts him back into training.

"I'm sure he will overcome this hurdle the same as all the others and he'll come back to racing and hopefully be even better again," Snowden said.