Sergio Aguero is set to miss the crucial tie against Liverpool this weekend.
The 32-year old striker has endured a frustrating campaign this season for Manchester City.
He missed the majority of the games in the new campaign as he was nursing with ankle and thigh injuries.
Earlier last month, he was forced into self-isolation when he came in contact with a Covid positive individual and then contracted the virus himself later in January.
Aguero has resumed full training this week but Guardiola believes he will need some more time to regain full fitness.
“He is still not training on the field,” Guardiola said.
“He started to move a little yesterday but he will need a few weeks to come back.
“He is negative, this is the most important thing. He is healthy again and now he will come back again. As the top scorer it is important for us to have him back.”
Sergio Aguero has entered the final six months of his contract and a contract renewal is on the cards.
Manchester City are currently leading the Premier League with a game in hand.