Rugby World Cup 2019: Over before it started - All Black Luke Jacobson's Cup dream shattered

The All Blacks have been hit by what they admit is their first setback of their World Cup defence in Japan: the ongoing concussion problems for Luke Jacobson which will force the loose forward on to an early flight home once he is cleared to get on the plane.

After three concussions in as many months, the 22-year-old will be out of the game for at least three months. A surprise selection in the 31-man squad given his inexperience, it's a cruel way for the young man's World Cup dream to end.

"I think you guys can imagine how I'm feeling," he told reporters from the team's base in Kashiwa ahead of next Saturday's opener against South Africa in Yokohama. "It's a bit of a tough pill to swallow. I found out last night and we made the decision that it's probably better for my career that I step away now and have some time to recover and hopefully put it all behind me."

Jacobson, who will be replaced by Shannon Frizell, said he may have received a knock in the All Blacks' recent test against Tonga in Hamilton which was potentially made worse by the 11-hour flight from Auckland to Tokyo. His most recent problem before that was a concussion suffered in training before the Springboks test in Wellington in July.

He said he didn't feel 100 per cent at training on Monday and Tuesday and the decision was made last night by coach Steve Hansen and doctor Tony Page that he would fly home as soon as he was able to.

"It's when I start to throw the ball around and run around that I start to feel it – just light-headedness, dizziness, you don't feel quite right," Jacobson said. "You drop a few balls and the skills aren't quite there.

"It happens, doesn't it? Throughout the World Cup there will be other people who are injured. It's not like I'm the only one it happens to. I just have to deal with it and get home. The support has been unreal from the management and the players and people back home."

Luke Jacobson has been ruled out of the World Cup. Photo / Getty

Page said: "He had a concussion last year with a prolonged recovery, so that's the background, and this year he's had three in as many months. There's no single number of concussions that would make you take the player out but our priority is his health and particularly his long-term health. We can't get caught up in the context of the World Cup. If this was a club player we would do the same thing."

"It's a hard conversation … but you look at the other side of it," Hansen added. "He's 22 years old and he's been selected for a Rugby World Cup. That's a ringing endorsement that he's got an outstanding career ahead of him."

Jacobson said he wasn't "scared" about the prospect of further problems but the enormity of recent events will force him to take it a bit more seriously.

"I've always shrugged it off," he said. "I probably haven't looked down the barrel at hit as much as I should have. I guess with this happening now … I don't think it's scary because there are a lot of players who have been in the same position as me like Ben Smith, Dane Coles, even Richie McCaw had the same sort of problems. It's comforting to have Ben and Dane around and to talk to them to hear how they got through it. I'm fully confident I'll be back out there playing."

Loose forwards Vaea Fifita and Dalton Papalii weren't available to replace Jacobson due to their own injuries. Hansen said Liam Squire, who had made himself available as an injury replacement in Japan after previously ruling himself out of contention, was not in the frame.

"Not really because nothing has changed," Hansen said. "It's happened right at the beginning of the tournament. We had the discussion and that was based around the time over here so nothing has really changed for him."

Hansen added: "Yes it's disappointing and it's a setback but you're going to get them. There's an expectation that we'll have injuries … you're challenged by those adversities but we've just got to get on with it."