Grealish posted an image of his mug, which appeared to show team-mate Ake with breasts, on his Instagram story with the caption: "What a cup of tea š & what a mug @nathanake ššš¤£š¤£."
The story has since been deleted.
Grealish spoke about Ake's impact at City in an interview with the club's official website on March 15. He said: "Nathanās so strong defensively and I think heās been unbelievable this season and one of our standout players.
"And I think a lot of City fans would say that also.
"Heās a brilliant guy and once of the nicest guys I have ever met in football and doesnāt have one bad bone in his body.
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"Heās someone I get on really with on and off the pitch. He works so hard every day on the training field and when he gets the ball, he just gives it to me all the time.
"And thatās what you want as a winger. You want your full-back to keep feeding you. But then when I am tracking back you feel so safe with Nathan behind us.
"Heās a great guy and Iām so happy for him because of the person he is. He is a lovely guy and so loved by everyone in the training room."