Aymeric Laporte was stretchered off during Manchester City's game with Brighton with an injury.
The Frenchman was late looking to poke the ball away from Adam Webster but crashed heavily to the ground and immediately signalled to the bench for medical attention.
After being treated on the pitch for an issue with his right knee, the centre-back was taken off the pitch on a stretcher with Fernandinho coming on to replace him and play his first minutes of the season.
Laporte's injury left Nicolas Otamendi as the only fit senior centre-back with John Stones having been missing since the opening weekend at West Ham.
City opted not to replace Vincent Kompany in the summer after refusing to meet Leicester's valuation of Harry Maguire, with Guardiola indicating that Fernandinho and youngsters Eric Garcia and Taylor Harwood-Bellis could help fill the position.
The Blues were leading Brighton 1-0 at the time thanks to Kevin De Bruyne's early goal. Sergio Aguero added a second shortly afterwards to make it 2-0 at half-time.
