Bellingham, the youngest member of Gareth Southgate's squad, excelled in an advanced midfield role during Tuesday's comfortable 3-0 friendly win over 10-man Ivory Coast.
"I haven't actually (played with a teenager who is that good)," Grealish said. "It is scary how good he is at 18.
"He is just so mature. He is built like he is my age at 26. He has so much technical ability and he is mature for his age.
"I can tell you one thing, I was nowhere near as good at 18. I was at Notts County (on loan from Villa) and I was a scrawny little thing as well.
"You see talented 18 or 19-year-old kids but not many are that mature as he is on the pitch. He is so versatile and can play in many different positions on the pitch.
"He can be a six, eight or a 10. It was good to play with him and I think it was my first time playing with him. It is nice to play with a fellow Brummie."
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