Gallas admits he doesn't believe his old manager is up to the job.
"Villas Boas, I've worked with him in Chelsea, in Tottenham and I do not think he's the man for the situation," Gallas told L'Equipe.
"Coach in Marseille? He could, but I do not think he has the shoulders strong enough to coach a team like OM. OM, it's really something different at the level of pressure, at the level of the supporters, at the level of what we will ask him.
"Personally I do not see him at OM because I think he does not have the build. It will be very difficult."