Brian McBride is set to be sidelined for three months after dislocating his knee.
The American forward picked up the injury as he scored for Fulham in their 2-1 defeat to Middlesbrough on Saturday.
He was immediately replaced by Diomansy Kamara and taken to hospital for scans.
Bouazza out for one month
McBride was accompanied in the ambulance by Hameur Bouazza, who suffered a shoulder injury later in the first half.
Fulham have now confirmed that Bouazza dislocated his shoulder and will be out for one month.
Club captain McBride is not expected to return to action until the middle of November.
"We lost two players with dislocations with minimal contact really," Sanchez said after the game.
"Brian scored and dislocated his kneecap in the doing of it with no contact whatsoever. We were dominating the game at that stage.
"Then (we lost) Hameur with an innocuous challenge to dislocate his shoulder."