Ba is thought to be upset at suggestions he is unwilling to sign a new deal.
And Bernard - who has worked closely with United's French stars - told the Evening Chronicle: "At no point would I be worried that Demba will leave the club.
"It's not like him, unless Newcastle are selling him.
"If they get another £35m then I suppose they would sell him.
"In terms of the man's commitment there should not be any worries because he's fully committed to the club.
"We can see that week in, week out. On the pitch he has been top-class. He's shown commitment and to his team-mates."