I covered a game at Swansea at the very start of the 2013-14 season. Manchester United won 4-1 but the abiding memory was of the peerless centre-back Rio Ferdinand suddenly looking much slower and older.
It was startling change over a short summer. Within half an hour the recent world class defender was being openly targeted as the weak link.
He wasn't awful, but clearly wasn't the 'Rolls Royce' that had previously cruised through games. Manager Alex Ferguson shockingly said afterwards that Rio had "lost a yard of pace". For a defender this is the beginning of the end, no matter how good or respected they are.
Rio was 34 years and nine months, Virgil Van Dijk is just two months short of that and sadly the miles on the clock are showing just a little more every week.
The first giveaway was when he started to 'go square' trying to tackle quick forwards, when previously he would have trusted his pace before and shown them wide.
Little judgement errors like Saturday's mis-control that led to the opening goal have crept in too.
One of the finest central defenders the Premier League has seen isn't finished yet and he is still the best centre-back at the club and currently capable of doing the job.
However Liverpool must scour the planet now for his replacement; the danger is that his abilities decline rapidly, just as Rio's did over the space of a couple of months.
He might not fall off the edge of that fitness cliff just yet – Thiago Silva lasted until just shy of his 40th birthday, but he was an outrageous outlier. But if the decline becomes more rapid with Van Dijk, Liverpool will be in severe trouble.
They must get at least one centre-back in this transfer window to safeguard their entire season.
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