Paris Saint-Germain came close to losing Kylian Mbappe for nothing in the summer after the France striker opted to run down his contract at Parc de Princes.
It was a nightmare scenario for the Ligue 1 champions and one that is set to become more common as the world's leading players opt to swap long-term security for the financial gains that come with lucrative signing-on bonuses and new contract negotiations.
Manchester United will lose a prized asset for nothing when Paul Pogba's contract expires on June 30.
Pogba can't lay claim to being United's highest valued player - Bruno Fernandes has that distinction - but it will still come as a huge blow to a club who shelled out around £94million for his services in 2016.
So, as the transfer window swings back into action, Planet Sport highlights the player with the highest market value from each of the 20 Premier League clubs and reveals the date they can depart for nothing.
Bukayo Saka (£58.5m) - contract expires June 30, 2024
Leading the way in the goalscoring charts with 11 and joint top of the assists with seven, Saka can justifiably claim to be Arsenal's most influential player - and the one that would cost the most to prise away.
Having signed a new contract in July 2020, Saka is tied to the Gunners until June 30, 2024.
Emiliano Buendia (£31.5m) - contract expires June 30, 2026
Having only signed last summer, Buendia is contracted to the Villans until 2026. Which is just as well as the former Norwich midfielder looks to be finding his feet at Villa Park with two assists and two goals coming in his last six outings for Steven Gerrard's side.
Ivan Toney (£31.5m) - contract expires June 30, 2025
His "F**k Brentford" rant forced Toney to issue a grovelling apology for a video which was "cut short and edited". However, with 12 Premier League goals to his name, the 2020 signing from Peterborough has plenty more seasons left in him at Brentford - if he replaces his video editor.
Yves Bissouma (£31.5m) - contract expires June 30, 2023
Bissouma has repeatedly been linked with a move away from Brighton but the reported £50million asking price kept those circling at bay - until the summer at least.
West Ham, Tottenham and Aston Villa are among the clubs who are monitoring his situation, with the midfielder out of contract in 2023 and the fee likely to drop dramatically.
Philip Billing (£16.2m) - contract expires June 30, 2024
Danish central midfielder Billing harbours ambitions to "play in a top team someday" which makes him a prime candidate to run down his contract at Bournemouth.
Turned down the chance to move to the Premier League last season with Norwich.
Romelu Lukaku (£76.5m) - contract expires June 30, 2026
Lukaku is contracted to stay until the end of June 2026 but on the strength of his performances this season he's as likely to leave in the summer as he is to make it through to 2026.
Lukaku scored just eight Premier League goals in 2021/22, which works out at around £12million a goal.
Wilfried Zaha (£36m) - contract expires June 30, 2023
Zaha is into the final year of a five-year deal and has shown no inclination to commit to a new deal.
Palace have previously priced him out of moves to Everton and Arsenal and this summer represents their last chance to receive a decent fee for him.
He will be 30 when his contract expires but would still command a great deal of interest from top-flight clubs, despite being the most dispossessed player in the Premier League.
Richarlison (£45m) - contract expires June 30, 2024
With Tottenham, Paris Saint-Germain and Real Madrid circling, it appears Richarlison may have kissed the Everton badge for a last time.
Dominic Calvert-Lewin (£37.8m) would then become the Toffees' most valuable player, although he appears to be on his way too.
Aleksandar Mitrovic (£18m) - contract expires June 30, 2026
Mitrovic's value was just over £14million when the Championship kicked off but 43 goals in 44 appearances have transformed his and Fulham's prospects.
Back in the Premier League, he will be looking to improve on his last top-flight season which produced just four goals.
Kalvin Phillips (£45m) - contract expires June 30, 2024
Would undoubtedly have left Leeds had they been relegated. However, the picture has been muddied by their survival. Phillips says he is keen to see out the final two years of his contract but with a switch in agents in the offing too and Manchester United one of the teams sniffing around, Leeds may choose to cash in and reinvest the money on striking reinforcements.
Wilfred Ndidi (£54m) - contract expires June 30, 2024
Ndidi only made 19 appearances for Leicester in an injury-curtailed season, with manager Brendan Rodgers pointing to his absence against Roma as a major factor in the Foxes' Europa Conference League exit.
Has been linked with a move to Manchester United but appears settled at Leicester. Rodgers certainly thinks so. "I know he's moved into a new house," he told the Daily Mirror.
Hopefully, it's not in Manchester.
Mohamed Salah (£90m) - contract expires June 30, 2023
Salah has yet to sign a new contract with Liverpool despite his current deal expiring in 2023. He says it isn't about the money and has pledged to remain at Anfield for next season. However, his future may be taken out of his hands if a new deal can't be struck with the Reds keen not to lose him for nothing.
Kevin De Bruyne (£81m) - contract expires June 30, 2025
The Premier League Player of the Season is tied to Manchester City until 2025 and seems determined to see his contract through.
"I've got another three years here, I'm definitely going to stay," he told fans at City's Premier League title parade. "This is where I want to be, where I want to win trophies, this is where we want to go."
Bruno Fernandes (£81m) - contract expires June 30, 2026
Fernandes only signed a deal in April to take him through to 2026 and has the option of an extra year on top of that. Reported wages of £240,000 a week will help cushion the blow of United's slide into irrelevance.
Allan Saint-Maximin (£28.8m) - contract expires June 30, 2026
"Right now I don't see myself leaving Newcastle," said Saint-Maximin in May.
However, while he is contracted to the Magpies until 2026 a number of interested parties may mean Newcastle choose to cash in on the Frenchman who for all his undoubted promise only provided five goals and five assists in 2021/22.
Brennan Johnson (£13.5m) - contract expires June 30, 2023
Wales boss Robert Page believes the 21-year-old is already good enough for a top-six club and with half of the top flight chasing him, an extension to his contract at the City Ground looks unlikely.
Forest's promotion looks set to keep him there for next season, though.
James Ward-Prowse (£28.5m) - contract expires June 30, 2026
A reported target for Erik ten Hag at Manchester United, Ward-Prowse only signed a long-term deal at Southampton last summer.
Another who is happy where he is: "I love being here and to be a part of this club is really special." However, at 27 and approaching his prime it looks like it is now or never for him if he wants to join a big club.
Harry Kane (£90m) - contract expires June 30, 2024
Depending on who you believe, Kane is either in talks with Liverpool or poised to make a dramatic U-turn and commit his future to Tottenham.
But after last summer's Kane transfer rumour overload, most neutrals have stopped caring where he ends up.
Declan Rice (£67.5m) - contract expires June 30, 2024
Chelsea and Manchester United's interest has prompted West Ham to offer Rice a staggering eight-year deal and a weekly wage of £200,000.
He appears to have rejected it but with David Moyes putting a £150million price on his head he is not going to be going anywhere any time soon.
Ruben Neves (£36m) - contract expires June 30, 2024
Manchester United are reportedly interested, with a £35million bid having been turned down in January. But Manchester United have been linked with just about everyone on this list so make of that what you will.
Wolves haven't given up hope of the Portuguese extending his contract at Molineux. However they will have their work cut out with rumours of a five-year deal being offered by Arsenal.