Former RB Leipzig boss Alexander Zorniger has warned that any Man Utd players or staff not pulling their weight will be replaced by Ralf Rangnick.
The German has taken over the reins at Old Trafford on an interim basis until the end of the season before moving aside to become a consultant for two years.
His reign has got off to a good start with two wins from two in the Premier League, moving Man Utd up to fifth, while they drew 1-1 with Young Boys in the Champions League.
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And Zorniger – who was chosen by Rangnick to become RB Leipzig manager – thinks some players and staff at Man Utd will get a rude awakening if they think Rangnick will take a few years to make changes at the club.
“Ralf hates wasting time – he wants to make the next steps,” Zorniger told BBC Sport. “If someone is thinking right now in Manchester United ‘well, it will take three or four years and then you will see the first influence’, no chance. If people are not doing what he expects, then he will replace them.
“He is the most improving professional I ever met. Every day he is checking everything: ‘Is that still state of the art? Do we need to improve something?’
“He always says football is a picture with 100 puzzle pieces and we should be able to provide all the 100 pieces to the players to become better players. That is what he is doing regarding nutrition, mental preparation, physical needs, physiotherapy, even checking hand-eye coordination, kinetics.”
Zorniger, who is now in charge of Cypriot side Apollon Limassol, added: “Ralf has always had the possibility to change everything. In Hoffenheim and Leipzig, he implemented a new coaching team, new players, a new medical department, a new scouting team.
“He doesn’t have these possibilities right now in Manchester United. These old, traditional clubs, they have an old, difficult network – and to open up and create new structures can be something really difficult.
“When he was appointed manager of Stuttgart in 1999, that was the first time he had to manage big players, and he was struggling because they didn’t follow everything he thought might be a good idea. But he has more experience as a coach now and knows exactly where he can change things immediately and where it takes a little while.”