Leeds winger Ben Jones-Bishop has been ruled out of action for up to six months while he undergoes treatment on a blood clot affecting his lungs.
The Super League champions announced that doctors have advised Jones-Bishop to rest for three months, avoiding all contact training.
Jones-Bishop, 24, said on Leeds' website: "It is obviously disappointing to miss the start of the season but I am looking forward now and doing everything I can to get back as soon as I can once I am given the all-clear.
"I am only able to do very light training at the minute and I will have another scan in a couple of weeks to see if I can increase that but I know I have to avoid contact for three months at least.
"It is a relief to get it diagnosed and get treatment and to know that it is not a life-threatening condition. Generally I am in good health but as a sportsman you need to resolve these issues as soon as possible to make sure that you can perform to your maximum."