Pogba played a crucial role for Didier Deschamps' triumphant side in Russia, and the 25 year-old star returned to United training on Monday ahead of Friday's opening Premier League fixture of the season against Leicester City.
LaLiga champion Barca is reportedly interested in taking Pogba to Camp Nou, with the transfer window still open until 1 September (NZST) for most of Europe's major leagues, while former club Juve has also been linked.
However, manager Mourinho affirmed that United have no intention of selling Pogba, who they paid Juve a reported £90million for in 2016, adding that the Frenchman may not feature against Leicester at Old Trafford.
"My perception, he arrived Monday, happy, proud, a desire to work," Mourinho said. "He worked amazingly well Monday, Tuesday, Wednesday. He's one of the players that I have to speak to, to see how physically and mentally he feels.
"But it's the same conversation as with [Ashley] Young, [Marouane] Fellaini, [Jesse] Lingard, it's the same.
"If they feel they can help us [against Leicester] – 20 minutes, 10 minutes, half an hour. We don't have many solutions and want to go with everything we have.
"I see [Pogba] very well but we need words with that small group to see if they can give us a hand. We have to try and get the best out of every player."
Mourinho was left frustrated in his attempts to bolster United's squad ahead of the season, as the club failed to bring in a central defender, with a late bid for Atletico Madrid's Diego Godin proving fruitless.