Van Dijk joined Southampton from Scottish Premiership champions Celtic on a five-year contract in the summer transfer window.
The 24-year-old centre-back struggled against Manchester United at St. Mary’s Stadium last month, but former Tottenham star Redknapp believes that he will prove to be a good signing for the Saints in the long term.
“At the back, Virgil van Dijk had a tough time against Anthony Martial but I think he'll be a good signing for them in the long-term,” the Englishman wrote on Skysports.com.
Van Dijk arrived in the Premier League with a strong reputation, having established himself as the best central defender in the Scottish Premiership.
The Dutchman has scored one goal and created one chance in three league games for Southampton so far this season.
The 24-year-old has a pass accuracy of 82% and a shot accuracy of 67%, and has won 15 headers, one dribble and three tackles.