The Welsh captain was not the only central defender targeted, though, as a move for Sunderland’s Lamine Kone fell through.
And it seems the Dutchman remains keen to add to his options as he is tracking another centre back, this time Ruben Semedo.
The 22-year-old is highly rated at the Portuguese giants and has starred for his country’s Under 21 side.
Capable of playing in defence or in defensive midfield he could fill several roles for Koeman.
A major stumbling block could, however, be his price tag, with the CalcioMercato report claiming he has a £40.2 million release clause in his contract.
His current deal does not run out until 2022 so Sporting would likely hold out for that price should Everton make any move in the future, which they are unlikely to do at that asking price.
With money to spend under Farhad Moshiri, though, perhaps a move could be on the cards should he impress the Blues scouts enough.