Guardiola believes the Argentine striker, who has 29 goals in all competitions so far this season, needs time to recover full match sharpness after his recent muscle problem.
However, Oleksandr Zinchenko won’t train this afternoon and he is a doubt for Wednesday’s game at the Etihad Stadium.
“I think everyone is fit,” Guardiola said. “I don’t think Zinchenko will train today, the other ones came back yesterday and are recovering well.
“[Fernandinho] trained yesterday, low intensity, but he trained.
“Aguero is fit. He needs competition and needs a little time to get best condition.”
City face a potentially season-defining week, starting with tomorrow’s Champions League quarter-final second leg, a tie that sees us trailing by a goal after last week’s 1-0 first leg defeat.
It’s followed by Tottenham’s Premier League visit to the Etihad on Saturday and the midweek trip to Old Trafford to face Manchester United.
And Guardiola says he is under no illusions about the importance of the games. Lose any, and he feels our hopes of an unprecedented Quadruple would go up in smoke.
"Definitely, if we don’t win these games, we lose the titles," he said. "This season we had an incredible opponent in Liverpool.
"Usually 84, 85 (points) is enough to win the title. We both deserve it but only one can get it.
"We will put our heart on the pitch tomorrow - our desire - and after we will see."