Virgil van Dijk has moved to ease those concerned about his short-term future. But Van Dijk is actually the only reliable centre-back option out of five. Van Dijk didn't just feature for every Premier League minute but he then went off the World Cup. That makes a big difference when it comes to longevity and Van Dijk rightly believes that could help him maintain his level for longer. So yes, there will naturally be concerns purely because what Van Dijk is trying to do is so rare.