PHILADELPHIA — When Michael Vick retreated to the end of Philadelphia’s bench after aggravating his strained left hamstring in the second quarter of the Eagles’ defeat against the Giants on Oct. 27, it seemed more than a game would be lost.

Nick Foles, Vick’s backup, was sidelined the previous week with a concussion after he completed only 37.9 percent of his passes in a loss to Dallas. Matt Barkley, a rookie from Southern California, failed to produce any points in either game, and the Eagles slipped to 3-5.

Just when it appeared Philadelphia had no one capable of leading Coach Chip Kelly’s high-octane offense, Foles, 24, asserted himself with surprising force. In doing so, he breathed life into his team’s season and altered a division Washington Redskins linebacker London Fletcher called terrible.

Foles, in his second season, enters Sunday’s N.F.C. East home game against Washington having erupted for an N.F.L. record-tying seven touchdowns in a 49-20 rout at Oakland followed by an efficient three-touchdown performance in a 27-13 victory last Sunday at Green Bay.