Jordi Alba and Gerard Pique both came off with injuries during the first half of the 4-0 win on Wednesday and were replaced by Lucas Digne and Jeremy Mathieu respectively.
Barca have revealed left-back Alba has suffered a hamstring problem and Pique has sustained an ankle sprain.
“The injuries to Gerard Pique and Jordi Alba – both were replaced during Barca’s win over Manchester City at Camp Nou – only serves to worsen Luis Enrique’s selection problems in defence,” read the club’s statement.
“Both players will have further tests on Thursday to ascertain the exact extent of their injuries.”
While the club are yet to release timescales, reports in Spain suggest Alba is set for roughly two weeks on the sidelines, while Pique is expected to miss around 10 days.
That would make them unavailable for the upcoming LaLiga matches against Valencia and Granada, before potential comebacks in the return game against City on November 1.