Cristiano Ronaldo has joined Saudi Arabian side Al-Nassr on a two-and-a-half-year deal that takes him beyond his 40th birthday.
The five-time Ballon d'Or winner, 37, is unlikely to play Champions League football again. Yet it's believed there's a plan in place for him to return to the Premier League if Saudi-backed Newcastle qualify for Europe's primary competition in the coming years.
The Magpies will reportedly bring in Ronaldo on loan if that scenario unfolds. The Portugal captain holds several records in the Champions League - including the most goals scored (140) - and it's claimed he wants to defend his achievements if possible.
That's according to Spanish outlet Marca, who have identified such a clause in Ronaldo's contract. There's a chance Newcastle will qualify for the Champions League because they are currently third in the Premier League - four points clear of Tottenham in fifth.
Perhaps the biggest sticking point in the proposal is the Saudi Professional League, which runs alongside European divisions (between August and May). Ronaldo would be unavailable for several Al-Nassr games if he joined Newcastle on a short-term loan deal.
Marcel Sabitzer completes Man Utd transfer after last-minute deadline day dashThe idea of Ronaldo joining the Magpies is unusual - but not unheard of. Here, Mirror Football takes a look at other bizarre contact clauses from years gone by.
What do you think is the strangest contract clause in football? Let us know in the comments below!
Barcelona famously included a clause in Luis Suarez's contract that stopped him from joining Manchester United. He left Liverpool to join the Catalan giants in July 2014 and it seems unlikely he would've joined the Red Devils, anyway, due to his Merseyside links.
Yet this clause put an end to all speculation, as Suarez wasn't even allowed to join United once his Barcelona contract expired. The Uruguayan was also prohibited from joining Manchester City, Paris Saint-Germain and Barcelona's bitter rivals Real Madrid.
Speaking of Barcelona, they broke the bank to sign Philippe Coutinho from Liverpool in a £142m deal in January 2018. The transfer proved to be a shrewd bit of business by the Reds, as the Brazil international failed to live up to his billing in Spain.
Yet the deal also effectively ensured Barcelona couldn't sign any more of Jurgen Klopp's players for the next three seasons due to a €100million (£89m) premium. This meant Barcelona would have to pay a transfer fee, plus this figure, to sign a Liverpool player.
Most footballers won't go anywhere near a nightclub during their playing days, but Ronaldinho wasn't an ordinary star. The Ballon d'Or winner loved to party during and a clause in his Flamengo contract, signed in 2011, allowed him to go clubbing twice a week.
It turned out to be a wise decision by Flamengo, as Ronaldinho scored 28 goals during the next 18 months and remained a Brazil international. Being disciplined is overrated!
While we're on the subject of mavericks, Neil "Razor" Ruddock was often the life and soul of the party during his career - something then Crystal Palace owner Simon Jordon was aware of when he signed the former England international from West Ham in 2000.
Jordan, on the advice of Hammers boss Harry Redknapp, inserted a 'recommended weight' clause in Ruddock's contract to ensure he remained in perfect physical condition. The defender would be fined by Palace if he went over 99.8kg on the weighing scales.
Man Utd deadline day live updates as Sabitzer completes loan moveJordan wrote in his autobiography: "I decided to put a 10 per cent penalty on the contract we were proposing to offer him if he was over the recommended weight of 99.8kg, which by the way was still frigging huge."
Ruddock reportedly breached the clause eight times in just one season.
This one probably isn't true. In a 2001 interview with Sky Sports, the Cardiff chairman Sam Hammam claimed new signing Spencer Prior - from Southend - was made to have "a physical liaison with a sheep and eat sheep's testicles" to prove his love for Wales.
Hammam bizarrely said: "It's simple. With Spencer being non-Welsh, he needs to prove to the people of Wales that he understands the place - then he can become a true leader."
Here's another clause involving Liverpool and Suarez. The Reds were angered by Arsenal's attempt to sign Suarez for £40,000,001 in the summer of 2013, with owner John Henry famously tweeting: "What do you think they're smoking over there at the Emirates?"
That prompted Liverpool to include an £89m clause in Roberto Firmino's deal when he arrived from Hoffenheim in the summer of 2015, yet Arsenal were barred from triggering it. That did the trick, as Firmino has remained a Liverpool player ever since.
Eintracht Frankfurt were willing to go the extra mile to sign Rolf-Christel Guie-Mien, an exciting 21-year-old midfielder, in the summer of 1999. They asked the Congo international what it would take for him to come to Frankfurt... and the answer was quite something.
Guie-Mien wasn't very happy with his wife's cooking and asked for the German club to pay for her lessons. He went to spend three years at Frankfurt, so we can only assume Mrs Guie-Mien established herself as Germany's answer to Delia Smith.
Manuel Neuer hit the headlines recently after breaking his leg during a skiing trip. Perhaps Bayern Munich should've taken a leaf out of Liverpool's book by inserting a no skiing clause in Neuer's contract, just as the Reds did when Stig Inge Bjornebye signed in 1992.
Bjornebye was a keen skier and his dad Jo Inge competed in back-to-back Winter Olympics during his heyday. The clause worked - as the Norwegian avoided an injury on the slopes - although he still had his fair share of knocks during his time on Merseyside.
The most famous clause in recent years involved Antoine Griezmann. He re-signed for Atletico Madrid from Barcelona in August 2021, yet the two-year loan included a clause that would see a permanent deal triggered if he played a certain amount of minutes.
Atletico were keen to avoid a hefty €40m fee, leaving Griezmann in a weird situation where he was only playing the final 30 minutes of games at the beginning of this season. In the end, the two clubs worked out an agreement, thought to be around the €24m mark.
Sunderland paid £4m to sign Stefan Schwarz from Valencia in the summer of 1999 - but only after he agreed not to become an astronaut. The small print of Schwarz's deal bizarrely read: "Space travel would see the contract terminated."
Sunderland's chief executive at the time John Fickling told the BBC : "One of Schwarz's advisers has, indeed, got one of the places on the commercial flights. And we were worried that he may wish to take Stefan along with him.
"So we thought we'd better get things tied up now rather than at the time of the flight. It was a reasonable request. We would normally get insurance cover for the player throughout the length of his contract. And like a lot of insurance policies, there are certain exclusions, such as dangerous activities.
"At the end of the day, we are protecting the club, really. It was a little bit of a light-hearted moment during protracted negotiations. But one day it could become be quite acceptable to put such clauses in various contracts."