Agents for Thiago Alcantara are pushing for an appearances clause in his Manchester United contract.
United are willing to meet Thiago's €18 million buyout clause in his Barcelona contract.
The Daily Mail says the 22-year-old's father, Mazinho, is thought to want a clause that will allow the Spain international to leave for a reasonable fee if he fails to reach a set amount of games in his first season.
Bayern Munich, Manchester City and Real Madrid are watching developments.