Ask Pep Guardiola, and he will say nothing has changed. Arsenal always had a game in hand in the Premier League title race, and Manchester City always took the view that the table was false until the top two were on the same number of games played.
Now, Arsenal have played that game in hand, beating Everton comfortably, and sit five points clear of City at the 25-game mark. Since losing to City, the Gunners have won three in a row, taking advantage of the Blues' slip-up at Nottingham Forest. They've shown they are not ready to give up the title and now it's game on, and City will be looking for their next opportunity to regain lost ground on Mikel Arteta's side.
It might not come until the final weeks of the season, though. Maybe even the final week.