The Englishman has been out of sorts for the past year, failing to impress in the Premier League.
While he was undroppable in 2023, as he helped his team to win the Treble, he is now a backup behind the likes of Savinho.
“It’s easy,” said manager Pep Guardiola after a win over West Ham.
“As much as he looks at himself, he will see the competition and that he has to compete, himself. Savinho is in better shape and everything than Jack and that’s why I played Savinho.
"I want the Jack that won the Treble? Yeah, I want it. But I try to be honest with myself for that. What happened with Savinho’s delivery in the box? It’s higher than the other wingers in that position and so they have to fight.
“You can say 'it’s unfair'. If you think that, then it’s fine. But you have to prove and say 'okay, I’m going to fight with Savinho, to deserve to play in that position every single day, every single week and every single month'.
“I fought a lot for him (Grealish), I fought a lot for him to be here, to do it again and do it again, and I know that he can do it, because I saw him. I've seen his level and I want that every single training session and every single game. If not, there's Savinho.
“Is there anyone in this room who thinks Savinho doesn’t deserve to play right now? No, he deserves to play. That’s why I play him - because he produces. So that’s why he played. I don’t have any doubt about the quality of Jack or any of these players, otherwise they wouldn't be here.
“But they have to, right now, today at 3pm, be at your best. It’s not about what they have done or will do, it’s about 3pm. The one hour 30 minutes, or one hour, 45 minutes that we're going to play, the responsibility belongs to the players, not to me, and they have to deliver, every single game.”