Kylian Mbappe and Erling Haaland may already be the game's next great rivalry, as some of us foretold three years ago. (I'm not taking credit for that one: it was hardly rocket science). But already what seems to set them apart from Lionel Messi and Cristiano Ronaldo is a keen awareness of who they are and the leverage they hold.

We had a reminder of this in the past week as speculation mounted over the futures of both Haaland and Mbappe, despite them inking new contracts in the past six months.

Media in Spain reported that when Erling Haaland moved to Manchester City this past summer, his agents made sure to include a release clause that would take effect in 2024. The Athletic later reported that the release clause -- which can only be triggered by clubs outside the Premier League -- stands at €200 million (£175m) and diminishes each season to the end of his contract in 2027.

On Tuesday, hours before Paris Saint-Germain's draw with Benfica, my colleague Julien Laurens reported that Mbappe was seeking an exit from PSG, with his family suggesting he made a mistake when he extended his contract in May, rather than leave as a free agent.

It's a stark contrast with their predecessors. Messi, of course, stayed at Barcelona for 18 years, and the prospect of his departure only really surfaced once he was the wrong side of 30. When he did move, aged 34 in 2021, it was amid a global pandemic, a financial meltdown and the tenure of a Barcelona president who was about as popular as bed bugs.

Ronaldo, meanwhile, left Sporting as an 18-year-old to join Manchester United. When he did agitate for a move back in 2008, he was told in no uncertain terms by Sir Alex Ferguson that he was going nowhere, at least for another 12 months. He transferred to Real Madrid for a world record fee in 2009 and ended up staying nine seasons.

Put differently, before the age of 23 -- which is how old Mbappe is now and how old Haaland will be next summer -- Messi and Ronaldo between them had moved once as professionals. Haaland is now at his fourth club, Mbappe at his second. But more than that, unlike with Messi and Ronaldo, at every stage there has been speculation over their futures.