Bravo is facing a lengthy lay-off after rupturing an Achilles tendon in training.
The only other back-up City have to number one Ederson is 20-year-old local Academy product Daniel Grimshaw. Neither Muric nor Grimshaw have made a first-team appearance for City.
City have been linked with Diego Cavalieri, the former Liverpool reserve who is now a free agent after leaving Crystal Palace, but Guardiola said that is not being considered.
The City boss said: “From then beginning it was Aro, Aro – that was the only option.
“The transfer window is closed so we cannot buy. With players who have retired – maybe – but when we knew it was possible for Aro to come back the decision was quick.”
Muric is likely to go straight onto the bench as the champions face Wolves on Saturday.
“We know him,” said Guardiola. “Last season he trained with us all season and he knows the way we work. We loaned him because the second team is not a real competition. We wanted to see him play every weekend.”
City are still unsure how long Chile international Bravo will be out for but the 35-year-old has undergone successful surgery in Barcelona.
Guardiola said: “I don’t know – but the surgery was good and we’ll see.”
Bravo himself has tweeted some pictures of his foot in a bandage following his operation.
“Thank you so much affection and concern,” he wrote.
Buenos días a todos, muchas gracias por tanto cariño y preocupación, en forma especial a los niños y funcionarios de @teleton ❤️Aquí estoy recuperándome gracias a todas las muestras de esfuerzo y sacrificio que me demuestran día a día.#VamosMuchachosQueSePuede #NoRendirse💪🏻 pic.twitter.com/00WjJ8aUGq— Claudio Bravo Muñoz (@C1audioBravo) August 24, 2018
The injury to Bravo was the second such blow City suffered in the space of a week after playmaker Kevin De Bruyne sustained knee ligament damage.
Guardiola feels the lack of pre-season training some players had this summer as a result of the World Cup is affecting his squad.
Speaking at a press conference, Guardiola said: “We are not far away but we’re still not fit.
“We see how much time the players need for regeneration after games. Normally it is quicker. They need more time.
“This is because we didn’t make a pre-season. After three or four days we played the Community Shield. A few players are much better but others need more time to win power and strength.”
City captain Vincent Kompany this week celebrated the 10th anniversary of his arrival at the club and he is set to make his 250th Premier League appearance against Wolves at Molineux.
Guardiola said: “Happy anniversary. It’s a long time, it’s many games. Unfortunately in the last years it wasn’t more.
“I’ve no doubts about his quality. When he is fit he is an excellent central defender. He’s a big personality and he’s loved in the locker room.”
City were taken to a penalty shoot-out by then Championship Wolves in the Carabao Cup last season.
Guardiola said: “They destroyed the Championship last season. They had an incredible season and they play in an attractive way. We know from the beginning how tough it will be.”
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Eden Hazard is in line for his first start of the season when Chelsea head to Newcastle on Sunday.
The Belgium World Cup star has come on as a second-half substitute in both matches so far, but boss Maurizio Sarri says he is now ready to play around 60 minutes.
Midfielder Cesc Fabregas looks set to miss out again with a knee problem.
Provisional squad: Kepa, Caballero, Rudiger, Alonso, Jorginho, Drinkwater, Kante, Barkley, Hazard, Pedro, Moses, Kovacic, Giroud, Zappacosta, Willian, Cahill, Christensen, Azpilicueta, Morata, Luiz, Emerson Palmieri, Ampadu, Loftus-Cheek, Hudson-Odoi.
The Gabon international missed two glorious chances during last weekend’s 3-2 defeat at Chelsea, which condemned the Gunners to back-to-back defeats in Emery’s first two games in charge.
Aubameyang, 29, is Arsenal’s record signing having joined from Borussia Dortmund in January and Emery feels the striker requires a boost in confidence to start scoring goals this season.
“Aubameyang needs to find the confidence, then to score and score another,” he said.
“The strikers, they need, I know a lot of strikers in my career and it’s about the moment, they need (to be in) the moment, and he’s the same.
“But I’m sure now that Aubameyang, (Alexandre) Lacazette, Danny Welbeck, they will score more goals in here, for us, in Arsenal.”
Aubameyang certainly did not struggle in front of goal in the second half of last season as the former St Etienne forward netted 10 times in just 13 Premier League outings for Arsenal.
“Last year, Aubameyang scored goals here and for that I spoke with him more times and I have given him my confidence with his work,” added Emery.
“He is going to find goals. The first six months for him here is good and he was doing goals last year and for that I am sure he is going to do the same this time.”
Aubameyang has been preferred to fellow striker Alexandre Lacazette in Emery’s opening two games, the Frenchman coming off the bench in the losses to Manchester City and Chelsea.
But, with West Ham the visitors to the Emirates Stadium on Saturday, Emery does not believe it is time to send out the duo as a strike partnership.
“At the moment, no,” he replied when asked if he could be tempted to play a front two against the Hammers.
“At the moment, I think we need to have the control with the possession, with the positioning on the pitch, with more players inside.
“After this possession, to do the attacking moments and defending moments with this balance.”