London - Wales coach Warren Gatland said he is "hugely worried" about George North's repeated concussions and fears further injury could end the 23-year-old winger's career.
The Wales and British and Irish Lions back has suffered four head injuries since sustaining concussion against New Zealand in November.
He was knocked out twice during Wales's Six Nations defeat by England in February before suffering the same problem in scoring a try for his club Northampton six weeks ago.
North has not played since the latest injury following advice from a neurologist and Gatland said he would prefer if North -- who has scored 22 tries in 47 tests -- continued his break until their World Cup warm-up matches in August.
"I had a meeting with George's agent and said if I was being purely selfish I would say; 'George, don't play in the last few games; get yourself right for the World Cup," Gatland told the Sunday Times.
"Because if he gets another knock he's going to have to be out for six months or a year.
"He has been out for a considerable amount of time but he's such a young player that if he picks up two or three more of those in the next year that's going to finish his career, isn't it?
"That is a concern, but I can understand Northampton being desperate to get him back playing, particularly as they get to the end of the season."
England fullback Mike Brown was knocked out during a Six Nations match against Italy in February and the 29-year-old continues to suffer from concussion symptoms 12 weeks since sustaining the injury.
He will not play for his club Harlequins again this season.