Everton suffered an early blow to preparations for their match against Manchester City after Bernard was injured in the warm-up and seen on the floor in agony.
The Brazilian was due to start the game at the Etihad Stadium in Everton's first match of 2020.
But during the Toffees' warm-up the winger was seen holding his left knee after being clattered into by Yerry Mina and looked to be in some serious pain.
Soon afterwards he went down and received treatment from the Everton medical staff, who tried to get him to his feet and run off the problem.
But the 27-year-old was soon seen shaking his head and headed for the changing rooms as the visitors completed their pre-game routine.
Fans posted videos of the aftermath of the incident on social media, with medicla staff gathered around the injured Brazilian.
However, confirmation of the extent of Bernard's injury have yet to be confirmed by the club.
The Brazilian was replaced in the starting XI by Tom Davies, with Anthony Gordon being promoted to the bench.
Bernard was set to start on the left-wing as Carlo Ancelotti made five changes to his side from their win at Newcastle.