Six Nations organisers have said that "a number of incidents" from Ireland's victory over France are being reviewed to see whether the head injury assessment (HIA) protocols were abused at the Stade de France.
French halfbacks Matthieu Jalibert and Antoine Dupont suffered knee injuries in the defeat but both were replaced under the HIA protocols. It allowed Machenaud to re-enter the game and replace Dupont rather than him having to be replaced by an unused substituted.
Irish fly-half Johnny Sexton questioned referee Nigel Owens on that replacement with four minutes remaining, but Owens insisted the match doctor had told him Dupont was leaving the field to undergo a HIA.
"The HIA Review Processor is reviewing a number of incidents from the France v Ireland match in the senior men's championship," Six Nations organisers said in a statement. "Depending on their findings, SNRL will be considering the next steps in respect of those incidents."
It is not the first time the use of the HIA has come under scrutiny, after France were reprimanded for failing to follow protocol in their victory over Wales in last year's tournament.
Among those critical on social media was former Irish captain Brian O'Driscoll who said the "it was nothing short of a disgrace".
Just because we won with an INCREDIBLE 42 METER drop goal that HIA decision shouldn't get swept under the carpet. It was nothing short of a disgrace!!!
— Brian O'Driscoll (@BrianODriscoll) February 3, 2018
Following last night's game against Ireland, French head coach Jacques Brunel stated the decisions were taken out of the his team's hands.
"They were collisions, but the head injury protocol was decided by the independent doctor; it wasn't our decision," said Brunel. "Both players had knee injuries, but the independent doctor decided that by the protocol."
The Press Association contributed to this report