McCoy is scheduled to undergo further testing on Tuesday, but is expected to become the team's second starting quarterback to see his season come to an end. Alex Smith broke his fibula and tibia in Washington's 23-21 loss to the Houston Texans on Nov. 18.
"This is a tough blow," Redskins coach Jay Gruden said. "Losing Alex was one thing. He was a great leader, great quarterback. Then Colt finally gets his opportunity and he gets kicked in the leg and breaks it. I'm heartbroken for both of those guys."
The 32-year-old McCoy completed all four of his pass attempts for 50 yards versus Philadelphia. He is 542 of 896 for 5,958 yards with 29 touchdowns and 26 interceptions in 38 career contests since being selected by the Cleveland Browns in the third round of the 2010 NFL Draft.
Sanchez completed 13 of 21 passes for 100 yards in the loss for the Redskins (6-6), who look to end a three-game slide on Sunday (1 p.m.) against the visiting New York Giants (4-8). The 32-year-old was playing in his first game since Jan. 1, 2017, as a member of the Dallas Cowboys.
"There's no excuses. To be totally honest, nobody cares. Nobody cares," said Sanchez, who was the fifth overall pick of the 2009 NFL Draft by the New York Jets.
"You're charged with a job. You get paid to play this game. You get paid to go win. That's what people expect."