Alex celebrates scoring Chelsea's second against Arsenal
Chelsea defender Alex is facing about three weeks out of action after picking up a thigh injury in the final stages of Sunday's 2-0 win over Arsenal.
The 28-year-old, who scored a spectacular 85th-minute free-kick, managed to complete the match.
But the Brazilian has withdrawn from his country's matches against Iran on Thursday and Ukraine on Monday.
He is also likely to be absent for Chelsea's visits to Aston Villa and Spartak Moscow on 16 and 19 October.
Signed from PSV Eindhoven in 2007, the centre-back has become manager Carlo Ancelotti's first-choice partner for John Terry at the heart of Chelsea's defence.
So far this season he has played every league game as the champions have begun their title defence in impressively miserly form - conceding only two goals in seven games.
Alex missed a month of pre-season training with a thigh injury, although it is not known if his latest setback is a recurrence of the same injury.
More to follow.