The International Rugby Board (IRB) has admitted some countries within the Six Nations are wary of adopting the global governing body's controversial pitch-side concussion assessment (PSCA).
IRB chief executive Brett Gosper of Australia is keen to have the PSCA in use during the next edition of Europe's Six Nations tournament, which starts in February.
However, Gosper said some countries within the Six Nations - which comprises England, Scotland, Ireland, Wales, France and Italy - still had to be convinced.
First trialled last year, the PSCA allows players to return to match action five minutes after a head injury as long as they have been cleared of concussion by medics.
To do so, they must answer a number of questions - without getting any wrong - and pass a balance test, otherwise they cannot return.
Previously, players had had to take three weeks off - later reduced to one week - if they suffered suspected concussion.
Former Wallabies team doctor, now IRB chief medical officer Dr Martin Raftery stressed the PSCA was designed only as a step-by-step tool to assess cases where concussion was not immediately apparent.
If a player was clearly displaying signs of concussion, he added, they shouldn't continue on in that same match.
The test has been trialled in leading tournaments, including England's Premiership and France's Top 14, but has met resistance from the Celtic League.
It has also drawn criticism from former Ireland international Dr Barry O'Driscoll, who claimed the issue of concussion was being trivialised.
"The Six Nations have not signed on to it yet and we are certainly putting pressure on them to adopt it," Gosper said on Monday.
"It is possibly because they have problems with PSCA but we will put pressure on those unions who are wary of it that these are the best protocols."
But, he conceded: "At the end of the day, it is their competition."
Raftery insisted the PSCA was leading to a reduction in the number of concussed players remaining on the field.
"In the past, 56 per cent of concussed players stayed on the pitch. Now with PSCA, it is down to 13 per cent. Is that good? No? Is that perfect? No. Obviously we want to reduce that figure even more."
Raftery also took issue with those who said five minutes was not long enough to properly assess if a player was concussed, labelling it a "poor argument".
"Five is better than zero. There isn't any question multi-modal assessment is the answer."
The PSCA was called into question during the deciding third Test between Australia and the British and Irish Lions in Sydney in July.
Wallabies flanker George Smith, clearly unsteady after clashing heads with Lions hooker Richard Hibbard in a sickening collision, returned to play after taking the PSCA.
IRB chiefs insist Smith should never have taken the PSCA as he was clearly concussed and there was no doubt about his condition.
International Rugby Players' Association chief executive Rob Nichol on Monday backed Raftery in saying five minutes was long enough for the PSCA and insisted his members weren't trying to cheat the system.
