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.