Cape Town - FIFA are investigating a complaint from Sporting CP relating to Rui Patricio's free transfer to Premier League newcomers Wolves last month.
The 30-year-old goalkeeper terminated his contract with the Lions after being attacked by ultras at the club's academy on May 15.
Patricio joined Wolves on a four-year deal just three days after representing Portugal in their 2018 World Cup opener against Spain.
However, the Portuguese outfit have taken exception to his move and contacted world football's governing body to deal with the matter.
"We can confirm that we have received a complaint from Sporting Clube de Portugal against Wolverhampton Wanderers and the player (Patricio)," a FIFA spokesperson told Omnisport.
"As the contractual dispute is currently under investigation, please understand that no further comment can be made at this stage."
Patricio made 46 appearances across all competitions for the Lisbon giants last season - his 12th at Estadio Jose Alvalade since coming through the youth ranks.