Pogba, 26, hinted at a move away from United last month when he said "it could be a good time to have a new challenge somewhere else," per David Hytner and Sid Lowe in the Guardian.
There has been little further progress on a potential departure, although Real Madrid reportedly have a "plan in place revolving around late transfer-window pushes for his signature," per Marco Ruiz of AS.
In the meantime, Pogba has been involved in United's pre-season preparations.
Mata said he is hopeful Pogba will remain at United despite his previous comments, per Simon Peach of the Evening Standard:
"We all know Paul, and he's a fantastic midfielder and he's a very good guy, very positive, good influence for everyone. I think he's happy. He brings everyone together.
"But I cannot speak for other people. ... And obviously as a team-mate, and as a friend also, I would like him to stay and to be happy because he is a very good player for us, but I cannot say much else."
Pogba re-signed for United from Juventus for a then-world-record £89 million fee three years ago.
His performances have been inconsistent ever since. At times he has been superb, but he has also been anonymous on some occasions.
Never was Pogba more frustrating than last season, when he enjoyed a fantastic two-month spell after Ole Gunnar Solskjaer's appointment but blew hot and cold for the rest of the campaign.
The France international's statistics were impressive, though, and showed how crucial he is for United:
If Pogba could produce his best more consistently, he would secure his spot among the best players in the world, and he could guide United back into the Premier League's top four.
It would be beneficial for United to keep him at the club, as he showed flashes last season that he can play at his talismanic best under Solskjaer.