Ronald de Boer believes Virgil van Dijk is now one of the best defenders in the Premier League.
Most notably, he has been impressed with the technical development the stopper has made since his time with Groningen in the Eredivisie.
Van Dijk – now a Dutch international – spent two seasons at De Boer’s old rivals Celtic before joining Southampton.
And he believes working under the likes of Ronald Koeman has turned the 25-year-old into one of the top players in the league.
He told TalkSport: “Under Ronald Koeman at Southampton he made unbelievable progress and now this year he is one of the top defenders in the Premier League.
“He has made the transition in a positive way.
“When he was at Groningen he did OK, he was physical, but we Dutch always want defenders to play the ball to the same colour and that is something we thought was not his best thing. But now he does that.
“His passing is excellent but, most importantly, his defending is outstanding. He is showing it week in, week out in one of the toughest leagues in the world.”
Van Dijk and his Saints team-mates are back in action this weekend when they travel to Sunderland on Saturday.