New Zealand back-row forward Luke Jacobson has been ruled out of the World Cup in Japan due to concussion.
The All Blacks said that 22-year-old Jacobson, who won caps against Argentina and Tonga this year, was suffering "a delayed onset of concussion".
Jacobson had travelled to Japan as part of the New Zealand World Cup squad, but he will now be replaced by the Highlanders' Shannon Frizell.
All Blacks coach Steve Hansen said Jacobson had not presented with any signs of concussion after last week's game against Tonga, but developed symptoms following a first training session this week.
"After discussing this latest episode with Luke, as well as our medical team, the decision has been made to, sadly, withdraw him from the tournament," Hansen told www.allblacks.com.
"We all felt that the best thing for him to do is to take a break from rugby until he is symptom-free and ready to return to rugby."