The signings that changed football
Some transfers win trophies. A few change clubs, leagues and the rules of the market itself.

Johan Cruyff to Barcelona (1973)
Cruyff's move from Ajax brought "Total Football" to Barcelona. His later spell as coach built the club's whole playing philosophy, the one that produced the teams of Guardiola and Messi.
Diego Maradona to Napoli (1984)
A world-record fee took Maradona to a club that had never won Serie A. Napoli won the league in 1987 and 1990: southern Italy's answer to the rich clubs of the north.
The Bosman ruling (1995)
Not a signing but a court case. Belgian midfielder Jean-Marc Bosman won the right to move for free at the end of his contract, and EU players could no longer be limited by nationality quotas. Player power and modern wages grew from here.
Cristiano Ronaldo to Real Madrid (2009)
A world-record fee for the time, and nine seasons in which Ronaldo became Real's all-time top scorer and won four Champions Leagues with the club.
Neymar to PSG (2017)
Paris Saint-Germain paid Neymar's €222 million release clause, more than double the previous record, and transfer prices across the market rose with it.