Now that the transfer window has closed and United was unable to add their squad last week, the emphasis is now on the current players.
And both Mata, 30, and Herrera, 29 on Tuesday, are out of contract at the end of the season.
It is understood that the two are disappointed that United has not given them new offers this year, since the club prefers to exercise 12-month options on their contracts.
But they have the opportunity to demonstrate to manager Jose Mourinho and executive vice president Ed Woodward that they deserve new deals.
There will be great interest in them, particularly in Spain, but both Mata (who has a restaurant in the city) and Herrera are still happy in Manchester.
Mata played in Friday night's 2-1 victory against Leicester at Old Trafford, but Herrera was lost to injury.