Grealish reckons Scotland international McGinn has the bargain buy of the season at just £2.5m.
Grealish said: “Ginny who has been unbelievable and is easily the buy of the season. I absolutely adore playing alongside him.
“He counts as two people and I don't mean the size of his head, either! Honestly, he is brilliant.
“He is such a good lad and so popular around the training ground. I said to him the other day I am not sure who I would choose between him and Fabian Delph.
“I loved playing with him when he was here and Ginny reminds me of him. The way they are both so eager to get the ball back and their work off the ball is incredible."
Grealish adds: “But both are great with the ball at their feet too He has given us a massive boost.
“When he was suspended I think he needed a little rest because he had played pretty much every minute. He needed the rest and now he has come back in he is unbelievable."