Any Chelsea deal to bring Barcelona star Lionel Messi could cost the club a staggering £500m (€640m).
There has been a lot of speculation in recent days linking the Argentinian with a move to the Blues or Manchester City as his future remains unclear.
Barcelona coach Luis Enrique has described reports of a bust-up with Messi as "inaccurate and ill-intentioned" after the pair were reported to have had heated arguments in training last Friday and again after Barca's defeat at Real Sociedad, where Messi was unhappy about being left out of the starting line-up.
Luis Enrique felt that Messi was not ready to start, having returned to training only on the Friday following his Christmas break.
On Monday, Messi then failed to attend a training session open to the public and a hospital visit to see sick children due to illness.
The fact that on the same day he started following Chelsea on Instagram was interpreted as another indication of his state of mind.
Today The Sun reports the enormity of any potential deal should Chelsea decide to pay the £200m release clause.
A further £300m would cover a six-year contract that would keep the striker at Stamford Bridge until 2021.
Former Barcelona assistant manager Henk ten Cate has claimed that Lionel Messi has remained at the Nou Camp because of a promise he had to Tito Vilanova on his deathbed.
"As far as I know, these problems all started about two years ago," he told De Telegraaf. "Messi is only still at Barcelona because he promised Tito Vilanova on his deathbed.
"But I think a transfer would be in everybody's best interest," he added.
It is the question that makes the rest of football's transfer window look like the offerings of a corner shop as it trails the prospect of the father of all epoch-ending mega deals.