Benfica president Luis Filipe Vieira has warned potential suitors that Axel Witsel will not be allowed to leave the club for a penny less than his release clause.
It was recently revealed that the Belgian international had a clause written into his contract that stated Benfica would have to accept an offer of £31m for his services.
The likes of Manchester United, Chelsea, Real Madrid and AC Milan have been credited with interest in the holding midfielder over recent weeks.
However, Vieira has insisted that they will not part with their player cheaply.
"Every club knows what his release clause is," Vieira told Antena 1. "If they come here and pay that fee, then there is nothing that we can do.
"We are very happy with Witsel and we do not think about selling him."
Witsel, 23, joined Benfica in 2011.
