Guardiola told reporters on Tuesday that Silva is doubt for Sunday's Manchester derby against United, but refused to specify the midfielder's problem, simply describing the issue as "something".
Fonseca, who has previously coached Porto and led Braga to cup success in his native Portugal, was linked with Everton before the Merseyside club appointed Sam Allardyce recently.
But the Spain international has not travelled for Wednesday's Champions League game against Shakhtar Donetsk, where Guardiola is expected to rest other key stars given his team have already secured progress to the knockout stages as Group F winners.
They followed up impressive wins at Watford and Arsenal with a 2-1 defeat of CSKA Moscow that sent them into the Champions League last 16 and have not lost at home since last year's loss to City - a run of 40 matches.
"I'm telling the truth, he's injured but will play for sure".
Manchester City's third successive late victory "shows what we are", manager Pep Guardiola said after David Silva's 83rd-minute winner saw his side equal a Premier League-record 13th successive triumph.
Dzagoev appeared to be in an offside position, but the goal was allowed to stand - credited to Vitinho - because Daley Blind was adjudged to have played him onside despite having slid off the pitch.
Mourinho's first season at Real Madrid in 2010-11 culminated in an infamously spiky series of matches against Guardiola's Barcelona, who would have the last laugh by claiming a La Liga and Champions League double.
John Stones and Benjamin Mendy are both injured but youngsters Phil Foden, Brahim Diaz, Tosin Adarabioyo and goalkeeper Danny Grimshaw have been included.
Guardiola added: "We just play to win the game".
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Kevin De Bruyne is suspended after collecting three bookings while David Silva, who is not fully fit, has also stayed at home. "I think that team won't be jumping with happiness to play against us". The way we control games is fantastic.
"He felt uncomfortable after his goal [against West Ham]".