Advertisement One of the countryâs top sports doctors believes the AFLâs new 12-day stand-down rule for concussions is âa backward stepâ that will not benefit player welfare. Sports doctor Nathan Gibbs during his time with the Wallabies. Nathan Gibbs, who has worked with some of the biggest sporting teams in Australia, including the Sydney Swans, Wallabies and NSW Origin and Australian Kangaroos, said once players had recovered from a concussion, there was no medical evidence that supported giving them extra time on the sidelines would reduce their chances of suffering another one. Gibbs also feared making players automatically sit out a game would set a dangerous precedent, especially around AFL finals time, and send âconcussions undergroundâ.