Gray reckons Grealish would represent a bargain at around £70m if United can get their money back on Paul Pogba - depending on how transfer values are affected by the coronavirus crisis that has brought football to a standstill.
“We don't know how football is going to come through this crisis," said Gray on the Keys & Gray show on beIN Sports.
“We don't know if football is going to be the same again and if it will affect players' values.
“But, when the dust settles, if I could sell Pogba for £100million and bring in Grealish for £70m, I'd do it in a heartbeat. It's a no-brainer.
“United still might be able to get their money back on Pogba. We know his value commercially and on social media with his millions of followers. That's important to football clubs these days.
“But he's pretty much failed at United. Is it his own fault or just bad luck with injuries? I think it's probably a combination of the two."