Standard Sport understands that Grealish, along with Leicester City’s James Maddison and Bayer Leverkusen’s Kai Havertz, is among United’s list of central midfielder targets, although signing winger Jadon Sancho from Borussia Dortmund remaining their top priority.
The Englishman has been heavily linked with a move away from Villa Park this summer, particularly if Dean Smith’s side are to be relegated.
But Djemba-Djemba believes Grealish would find himself sitting on the bench, however.
Speaking to BettingApps.com, Djemba-Djemba said: “I think that Fernandes and Pogba are both a lot better than him, so he would be joining as a substitute.
“He would struggle to start over Rashford, Martial or Greenwood as well, but he would definitely be a good signing.”