Jamie Redknapp says Tottenham will show a lack of ambition if they fail to keep Mauricio Pochettino, but expects the Argentine to join Manchester United in the summer.
Pochettino is favourite to become United's next permanent manager in the summer after Ole Gunnar Solskjaer was installed on an interim basis until the end of the season.
"I think Manchester United will get him (Pochettino). I think they will go for it and I think they will get him," Redknapp told Sky Sports Football.
"Of course [Spurs fans should be worried] because he's the special one, he's a great manager that everyone would want at their club.
"Tottenham have got to do everything in their power to keep him, it's as simple as that. He's a very talented manager, the players adore him and play for him and you can see why Manchester United would want him."
However, Redknapp believes it would be a wrench for Pochettino to leave so soon after signing a new five-year contract in May.
"It is all there for him [Pochettino], moving into a new stadium, a great young side and if he was to move it would be a real shame for Tottenham.
"But I'm sure, knowing Daniel Levy, he will think 'where is the next one, who is the next manager that could take this club forward?'
"He will know there are people out there. There are not many like Pochettino but I would say someone like Eddie Howe would be the perfect fit for Tottenham; he gives young players an opportunity.
"So I don't think it will be the end of the world but it will be a huge blow because it will give a lot of players the opportunity to say 'if he's gone we might want to go as well'.
"They have to keep him, it's as simple as that. Tottenham have let a lot of their best players go in the last 20 years but they can't let their best manager go because he's a special talent. It would show a lack of ambition if they did let him go."