Gullit, who took charge of the club in August 1998 before being sacked 12 months later, claims Keegan will find it difficult to attract good players to the club.
Gullit Says Job Is Too Big For Keegan!
Gullit: "No, he won't do it. It is not realistic to expect that.
"For the simple reason that the other clubs have a huge advantage because they have the best youngsters and the best players in all these other teams. So it is going to be difficult and it is not realistic.
"A realistic goal is that he needs to have the time to build a team and maybe then in the future they can compete in the league.
"I think the expectations at Newcastle are so incredibly high that maybe they are not realistic for the people who go to work there.
"For the simple reason that the other clubs have a huge advantage because they have the best youngsters and the best players in all these other teams. So it is going to be difficult and it is not realistic.
"A realistic goal is that he needs to have the time to build a team and maybe then in the future they can compete in the league.
"I think the expectations at Newcastle are so incredibly high that maybe they are not realistic for the people who go to work there.
"Newcastle is such a big club and I think they have had great coaches and some big names - Sam Allardyce, Glen Roeder, Graeme Souness, Bobby Robson, Kenny Dalglish - and therefore it is not about the coaches, it is much more complex than that.
"With Sam Allardyce it was incredible - once he was talked of with the national team and now nothing, and I think again they haven't been realistic there with him. It is not possible there, just not possible.
"Also you have the local press, who have big expectations and big ambitions, and it is not realistic what they ask.
"The most difficult part is that they have to compete with teams who are much more attractive than Newcastle are.
"Most big players and promising young players go to Manchester United, Chelsea, Liverpool and Tottenham.
"It means that none of the biggest players want to go there (Newcastle) which is a major a difficulty that you have to deal with."