Rafa Benitez has explained his decision to sell Chancel Mbemba to Porto.
The Newcastle United defender was sold ahead of Saturday's friendly between the two sides at the Estadio do Dragao.
Mbemba, 27, had been sidelined by Benitez at St James's Park for much of the past two seasons.
Asked about the sale, United manager Benitez said: “We're talking about a player where we know he has quality if we analyse him technically.
"After, you have to settle down in the team, the city and the country. All these things together can make a big difference to the performance of a player on the pitch.
"We had Jamaal (Lascelles), (Ciaran) Clark and (Florian) Lejeune doing well, so he didn’t have his space (in the team). There is an opportunity for him now to go to an important club and do well."
Benitez is now pushing for a replacement. “We have to strengthen everywhere," said Benitez.
"If we want to compete in the Premier League, we have to be stronger. It's as simple as that."
Lejeune is sidelined with a knee injury ahead of the Porto game.