Grealish endured a frustrating afternoon on Merseyside with Liverpool and City fighting out a thrilling 2-2 draw at Anfield.
The former Aston Villa captain was replaced after 66 minutes however with Raheem Sterling brought on as City chased an equaliser.
Grealish also came off with 20 minutes of the game left in similar circumstances midweek in the Champions League against Paris Saint-Germain.
With Phil Foden, Bernardo Silva, Riyad Mahrez and Raheem Sterling also jostling for positions in City’s attack, Keane suggested Grealish will have to continue fighting for his place in the team.
‘With all the attacking players Pep [Guardiola] has got they will just have to rotate and be part of the squad,’ Keane told Sky Sport.
‘You have to adapt if you want to be a top player including Jack Grealish who is still new to Man City.
‘And Jack has had a tough week. Some of his performances, against PSG was really tough in the week, lads were getting stuck into him.
‘He gets taken off here today, he is 26 years of age so he’s got to man up.
‘Because Pep will be saying: ‘You are here to win big prizes.’ People like jack are still learning.’
City’s draw at Liverpool means Chelsea head into the international break top of the Premier League with a one point lead over Jurgen Klopp’s side.
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