Eric García and Jules Koundé have both been ruled out of Barcelona's Champions League game against Paris Saint-Germain on Tuesday.
García will also miss Sunday's Clásico against Real Madrid after being ruled out for up to four weeks with a thigh injury picked up in Saturday's win at Real Betis.
Koundé will be assessed ahead of Madrid's visit to Spotify Camp Nou in LaLiga this weekend after spraining his ankle in the same game.
The loss of García and Koundé leaves Barça coach Hansi Flick without either of the players he has used at right-back this season.
However, João Cancelo and Xavi Espart, both used as left-backs this year, can play there, as could Alejandro Balde.
García's injury also leaves Barça short at centre-back, with Andreas Christensen currently out with a thigh issue, too.
That leaves Pau Cubarsí and Gerard Martín as the only available central defenders in the squad ahead of Tuesday's showdown with the European champions.
Midfielders Rodri and Frenkie de Jong have also played there in the past, with Flick confirming the Dutchman could be an option at the back after he returned to training last week.
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Elsewhere, following De Jong's return to the matchday squad at the weekend, Barça are in good shape ahead of the biggest week of their season so far.
Captain Raphinha returned off the bench against Betis and will be available for Tuesday's game in Paris and Madrid's visit on Sunday.
Barça are seeking to maintain their perfect start to the season in France after winning all 11 of their matches in all competitions to date.