Sergio Aguero will be out of action for up to 10 days because he has to self-isolate, according to Man City boss Pep Guardiola.
Aguero was expected to start in last weekend's FA Cup third-round tie against second-tier Birmingham City but did not feature in the matchday squad as City won 3-0.
City's record scorer has played nine games in all competitions this season after missing the start of the campaign following knee surgery.
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"He's isolating," Guardiola told reporters before Wednesday's Premier League game at home to Brighton & Hove Albion. "(He is following) the rules. After nine or 10 days he will be back."
City, who are fifth in the table with 29 points from 15 games, have midfielder Raheem Sterling available after he was left out of the last game due to lack of match fitness, but defenders Aymeric Laporte and Nathan Ake are still injured.
Defender Eric Garcia and midfielders Adrian Bernabe and Cole Palmer are still in isolation, Guardiola said.
City have won their previous six games in all competitions, including wins at Chelsea and Manchester United, but Guardiola said his players must guard against complacency.
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"The momentum arrives and disappears in one instant," he added. "We cannot forget the teams we beat recently, especially in the Premier League... But the momentum can disappear tomorrow so we have to do it again."
The Spaniard said City face a tough challenge against Graham Potter's Brighton, who are 17th with 14 points after 17 games.
"Brighton are a joy to watch and analyse," he added. "I said to the players we have to be at a high standard to beat them.
"Forget the results we had in the past - they are better in all departments. They create more than they conceded."
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