Red Bull boss Christian Horner has admitted that Formula 1's former Race Director, Michael Masi, applied safety car rules "differently" during last season's Abu Dhabi Grand Prix.
Red Bull's Max Verstappen was crowned as the sport's newest World Champion following 2021's final round, after a late-race Safety Car bunched the pack up, handing him the chance to pass rival Lewis Hamilton for the win on the last lap of the last race.
Few could grumble at Masi's decision to call for the Safety Car after Nicholas Latifi crashed badly at the Yas Marina Circuit, but with only a single lap remaining and with lapped backmarkers still scattered amongst the grid, the Australian made the decision to resume the race by removing only the lapped cars between Verstappen and Hamilton.
That left the two championship protagonists to fight it out at the front for one final lap, leading to an unforgettable spectacle for fans, but Carlos Sainz, in third and stuck behind lapped cars, was unable to fight for the win himself.
The call also left Mercedes - unable to pit at risk of losing track position to Verstappen during a race that they expected to end behind the Safety Car - out on used tyres, while Verstappen, in a position with all to gain and with nothing to lose, was able to pit for fresh, faster tyres.
Hamilton branded Masi's late-race decision to end the Safety Car early as race "manipulation" via his team radio, while Red Bull celebrated what they saw as a race-winning pit stop strategy.
Horner adamant Masi broke no rules
Mercedes appealed the decision immediately and argued that Article 48.12 of Formula 1's sporting regulations had not been followed as the Safety Car did not complete an extra lap following the removal of lapped cars before returning to the pits.
But that appeal was thrown out with Article 15.3 having handed the Race Director ultimate control over the use of the Safety Car, including when it is called back to the pit lane.
Masi has since been removed as Formula 1's Race Director with a promise made by the FIA to find him an alternative role within their organisation, while the above Safety Car regulations have since been tweaked.
The FIA are expected to this month release a report setting out their findings following an investigation that Hamilton has demanded be published in full.
Red Bull, meanwhile, remain adamant that no rules were broken in Abu Dhabi, but now Horner has admitted that he believes Masi instead applied said rules "slightly differently".
Speaking to Sky Sports F1 in a clip from their soon-to-be-released documentary 'Duel: Hamilton v Verstappen', Horner said: "He didn't break the rules.
"He perhaps applied the rules slightly differently in that circumstance but there was nothing he did that actually contravened the rules."
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Verstappen: Masi needed more support
Masi has since been replaced by a new Race Director structure in Formula 1, set to be implemented for the first time during the upcoming Bahrain Grand Prix.
Niels Wittich and Eduardo Freitas will act alternatively as the Race Director, assisted by Herbie Blash as a permanent Senior Advisor.
And new FIA President Mohammed Ben Sulayem has vowed to introduce a refereeing room, compared to football's Video Assistant Referee, to make live calls on in-race incidents.
But Verstappen believes that Masi needed more support, both in his role and dealing with the online abuse that followed his exit.
"You can always argue was it right, was it wrong, what he did in Abu Dhabi," Verstappen commented.
"I think what Michael stood for was always racing."