In 2005, 4.5 concussions were reported for every 1000 hours of professional rugby in New Zealand. By 2013, that number had jumped to 9.6 per 1000 hours and, while data has not been released for the season so far, the number of players who have suffered a concussion is extensive.
Jerome Kaino, Kieran Read, Richie McCaw, Sam Whitelock, Ryan Crotty, Conrad Smith and Sonny Bill Williams have all been sidelined.
It's hardly a wild guess to say plenty of critical players will suffer a concussion during the World Cup. It will happen and, when it does, the pressure will be on every coach to prove they are committed to their players' welfare in practice as much as they say they are in principle.
A seven-week tournament, with everything at stake - creates its own pressure. Coaches will want their best players to be fit.
The players, too, knowing World Cups are only every four years, will be just as eager to be fit and a concussion could be viewed by some as decidedly inconvenient.
That's the worry for World Rugby. For all the progress they have made in converting the trial concussion protocols into law and improving attitudes, when the stakes are at their highest, will everyone take their duty of care as seriously as they should?
"We don't care that it's a World Cup as we have clear expectations about standard behaviours around concussion," says International Rugby Players' Association chief executive Rob Nichol. "But given the profile of the World Cup, the examples set there in how teams deal with concussion will really set the tone. There's no doubt that what happens at the World Cup can permeate through rugby. Medics, coaches and players have a key role to play in driving the culture change."
Game day isn't the big concern. It's nearly impossible in a test match for a head knock not to be picked up and for the compulsory testing to follow. The match doctor has to witness the testing and agree to let the player return - so that process can't be abused. But it's what happens after that.
There is best-practice advice and guidelines for medical staff to follow so a concussed player can resume playing. But there is no requirement to submit concussed players to independent testing. Essentially, the return to playing is entirely dependent on coaching and medical staff accepting they have a responsibility to show duty of care to the athlete.
The All Blacks have had their welfare conviction tested in recent years and shown total resolve. Read was forced out of the series against England last year when the All Blacks didn't have a natural replacement at No8, and Brodie Retallick was sent home from South Africa which meant they played at Ellis Park without a specialist lock on the bench.
The All Blacks have a proven track record of not risking any player's health regardless of the occasion. Their commitment to protect players is genuine. But will other teams be similarly committed if faced with the prospect of losing a key player for a knockout game?
That's the question that can't be answered until the pressure of the occasion comes to bear on the respective teams. What coaches say now is not by any means what they will do in September and October and World Rugby can only hope the outcomes are good for the game.
The World Cup presents the game with an opportunity to drive home to a huge global audience that concussion is serious and the health of the players is never to be compromised. There could be no more powerful reinforcement of that than big-name players who suffer a concussion being left out of the biggest games.
Conversely, there is no bigger threat to the game's integrity and standing if players concussed one week are declared fit the next.
