Marco Silva confirmed Bernard sustained a knee injury during Everton's defeat at Brighton but said it was "too early" to know the severity of the problem.
The Brazilian limped off after slipping awkwardly on wet turf after half an hour at the Amex Stadium and was replaced by Gylfi Sigurdsson.
Bernard will now continue to be assessed by the Club's medical team at USM Finch Farm.
"It is too early for updates," Silva told evertontv at full-time. "He felt something in his knee. Let’s see in the next few hours and days how he will be. I will wait for the medical staff to give me more information."
Silva was without Yerry Mina for the game on the south coast after the Colombian failed a late fitness test.
The defender had limped off late in the Blues' 2-0 win over West Ham last weekend after picking up a minor knee problem.
"Yerry was not ready for the game," said Silva. "He tried this morning to see how it was, maybe to go to the bench, but he was not in condition to [play]."
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