Kevin De Bruyne will be out of action for four weeks with a hamstring injury he picked up on 24 September, according to the Mirror Online.
The Manchester City playmaker was assessed by a doctor on Sunday but a full prognosis is not expected by the club until Tuesday.
De Bruyne limped off the field in the 81st minute of their side's 3-1 win over Swansea City on Saturday. Before coming off, he had drawn a foul in the penalty area which led to Sergio Aguero's second goal of the day as The Citizens clinched their sixth straight Premier League win of the season.
A four-week layoff could see the 25-year-old miss Wednesday's Champions League encounter against Celtic and Premier League games against Tottenham Hotspur and Everton. He would also be not available for manager Pep Guardiola's return to Camp Nou for their high-profile encounter against Barcelona on 19 October.
Also, he would not be part of Belgium's squad for the 2018 Fifa World Cup qualifiers against Herzegovina and Gibraltar on 7 and 10 October, respectively.
Reacting to De Bruyne's injury, Guardiola insisted his side needed to keep their winning momentum going into tough fixtures even without their key player. Notably, under the Spaniard, City have started the 2016/17 season with 10 straight wins in all competitions.
"Kevin is not going to play the next games and now we need to keep going and win the games without him," Guardiola was quoted as saying by the Mirror Online.
"We have to do that. We are here to get better. You always have to keep going. It never ends in football.
"You can always improve - individual performances, collective performances. You can always create different things and that's why the game is nice."