Starting left guard Kory Lichtensteiger suffered a knee injury on the first drive of the game.
Injuries happen in the NFL, and they can never excuse a loss. That being said, the Redskins were missing some key players for Sunday's game.
Shanahan entered the game without two starters: running back Tim Hightower and cornerback Philip Buchanon. Hightower's replacement, Ryan Torrain, had 10 carries for only 22 yards, and the Redskins could never establish a running game (which is actually probably Grossman's fault as well).
Buchanon was replaced by nickelback Josh Wilson, and Kevin Barnes moved into Wilson's spot. The Redskins struggled in pass defense early, and gave up a much higher percentage of third-down conversions than they had all season: 37 percent on Sunday compared to a league-leading 26 percent entering the game.
Also hampering the Redskins' defense was the toe injury of free safety Oshiomogho Atogwe, who was listed as probable on the NFL injury report entering Week 6. Atogwe played but did not appear able to run at full speed, and was spelled by backup Reed Doughty later in the game.
Atogwe has had a terrific season, but his ineffectiveness on Sunday contributed to the problems in coverage.
The Redskins' offense took a huge blow when tight end Chris Cooley was injured during Washington's second possession, another bad play Grossman can take credit for.
On a 3rd and 2, Cooley was led by Grossman right into a massive hit delivered by Philadelphia corner Nnamdi Asomugha. The play resulted in a one-yard loss, but more importantly Cooley broke his index finger on the play and could miss up to several weeks.
Offensive coordinator Kyle Shanahan's game plan included lots of two tight end sets designed to exploit the weak linebackers of the Eagles, and the loss of Cooley limited his ability to do so.
The Redskins also lost starting left guard Kory Lichtensteiger, who went down with a knee injury on the first drive of the game, and later lost left tackle Trent Williams to a high ankle sprain.