The pair have been at the club for a few seasons now with both their contracts set to expire in the upcoming months.
Herrera had proven himself to be a crucial player under Ole Gunnar Solskjaer’s management before he suffered an unfortunate injury.
Mata hasn’t been a key part of the Norwegian’s system but his playmaking ability has made him a useful rotational player.
United could be without either one by the start of the next season which is enough of a loss in and of itself but having been unable to make some money out of them is equally bad.
According to TalkSport, the Mirror report that the duo’s agents have been attempting to get their clients a pay rise with the Red Devils unwilling to comply.
Vice-Executive chairman Ed Woodward has had a similar problem with many of the club’s players with some reports claiming Alexis Sanchez has caused this issue.
The belief is the Chilean’s incredible wages has set a new benchmark for what many of the Manchester United players believe they should earn, making all negotiations difficult to conclude.