"We return to training with the mindset on the Newcastle match and the importance of the months that lie ahead, as they come loaded with games, especially during the Christmas period," Mata wrote on his blog on the club's website.
"These are moments in which good form of the team can be decisive for the second part of the season."
Mata, who has not featured in the league since last month's 2-1 loss at Huddersfield Town, said United had to guard against complacency against Newcastle.
"Everyone knows they are newly-promoted but they are still a big club with several Spanish players ... We hope to play a good game that allows us to get all three points, and continue showing that strength in Old Trafford."
(Reporting by Shrivathsa Sridhar in Bengaluru; Editing by Peter Rutherford)
