The midfielder is said to have sustained a muscular injury and will now miss Wednesdayâs big game against Pep Guardiolaâs side.
Partey has been one of Arsenalâs standout performers this season and is one of the main reasons why the Gunners sit at the top of the table.
The Ghana international played 18 Premier League matches this season for Mikel Artetaâs side, contributing two goals thus far.
According to a report by The Athletic, the midfielderâs injury is not serious but the club has decided to take precaution by not risking him against Manchester City.
Meanwhile, Arsenal are currently just three points above Guardiolaâs side ahead of Wednesdayâs all-important meeting between the two teams.
Should Manchester City win the game, they will overtake the Gunners at the top of the table on goal difference, although Artetaâs side has a game in hand.
Thomas Partey has been exceptional for Arsenal this season
Speaking ahead of the game, the Arsenal manager said his side is aiming to return to winning ways after failing to win each of their last two league matches.
âWhat they [City] have done in the last six years, they absolutely merit it,â Arteta told the media.
âThe way they play, the way they have competed, the way they have gone through difficulties. For us the challenge is to get to that level.â
Meanwhile, Arsenal could pull six points clear at the top of the table if they win against Manchester City.