Angel di Maria had an anti-Barcelona clause written into his contract when he joined Manchester United from Real Madrid, according to website Football Leaks.
The Argentina international now plies his trade at Paris Saint-Germain, but spent one season at Old Trafford after the Red Devils spent £59.7m to buy him from the Bernabeu in 2014.
According to the whistle-blowing website, both parties agreed that Madrid would receive €1m (£778,790) if Di Maria was part of a Champions League-winning squad at Old Trafford and €5m (£3.8m) if he was named in the top three of the Ballon d'Or awards.
It has also been claimed that United would have lost €30m (£23m) if they opted to sell Di Maria to Barcelona before the expiration of his contract, but any other La Liga club, the fee would have reduced from €50m (£38m) each year.
United sold the Argentine to PSG last summer for a reported £44m fee.
