Mbappe, Messi, Sancho and the top 25 most valuable players

Transfer season is upon us, with several clubs already making big moves for big players to kickstart the summer. However, one major question still remains: who is the world's most valuable player?

Neymar's move to Paris Saint-Germain remains the most expensive transfer in history, as the French side forked over €222 million (£200m/$263m) to sign him from Barcelona in the summer of 2017. 

Still, the Brazilan winger is no longer considered the most valuable player on his own team, let alone in the world, as a number of young stars have risen up the ranks.

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CIES Observatory has aimed to answer the question of who is currently the world's most valuable star as they ranked the transfer value of all the footballers in the top leagues by an algorithm that accounts for a variety of factors, including age, production, current league and contract.