Chelsea have suffered a fresh injury setback with the news that Alex is facing six to eight weeks on the sidelines.
The Brazilian missed the shock 3-0 defeat to Sunderland on Sunday, along with fellow first-choice centre-back John Terry.
Reports have since emerged that Terry could be out for months with a nerve problem, although he will see various specialists in a bid to find a solution and return quickly.
But the Blues have now been struck another defensive blow with Alex set to undergo surgery on his right knee.
The 28-year-old had joined up with his national team for Wednesday's game against Argentina in Qatar but has now pulled out.
Chelsea's medical team have decided that further investigation via arthroscopic surgery is required and Alex could now be out for almost two months.
He will therefore have to sit out a number of crucial Premier League games before a possible comeback at the turn of the year.
Alex has established himself as a key player since arriving at Stamford Bridge in 2007, especially since the departure of Ricardo Carvalho this summer.
Carlo Ancelotti will have to rely on others without Alex and Terry at his disposal, although makeshift pair Branislav Ivanovic and Paulo Ferreira struggled against the Black Cats at the weekend.