Manchester City manager Pep Guardiola has said he must look for more defensive options because Fernandinho and Nicolas Otamendi are too old to play every game.
With City in the midst of an injury crisis in defense, the pair started Wednesday's 3-0 Champions League win over Shakhtar Donetsk.
Riyad Mahrez, Ilkay Gundogan and Gabriel Jesus all scored as City got their Champions League campaign off to a flying start, but a shortage of healthy centre-backs still looms over the club.
Aymeric Laporte is set to miss up to six months with a knee injury and John Stones is out for five weeks with a muscle problem, leaving City in a major bind at the back.
Defensive mistakes – particularly one by Otamendi – were prevalent on Saturday as City fell to a shock 3-2 defeat at newly-promoted Norwich City.
Otamendi is the only healthy natural centre-back in the squad meaning Fernandinho, a regular midfielder, has been asked to deputise at the back.
But Guardiola has suggested that because of their age, he will also have to call upon midfielder Rodri and right-back Kyle Walker at centre-back in the coming weeks.
"I didn't have doubts [Fernandinho] could do it," Guardiola said after City's win on Wednesday. "Nico is 31, Fernandinho is 34 and the next alternative (Eric Garcia) is 18. For three or four months I don't know what will happen.
"Both were incredible tonight. Nico showed incredible personality after what happened in the previous game.
"We need another solution -- Rodri or Kyle Walker maybe -- because they cannot play every game at their age."
Fernandinho, who was making only his second appearance of the season on Wednesday, said after the game that he was comfortable at centre-back and ready to play the position as much as his manager requires.
"I've been training in this position since the start of the season. Pep knows all about our squad and team," the Brazilian told BT Sport.
"Today was my opportunity and I hope I can improve more."
City will return to Premier League play on Saturday when they take on Watford. Their next Champions League match will come on October 1 when they host Dinamo Zagreb.
