The Caps took a 1-0 lead midway through the first period when Stanislav Galiev drew the Flyers' defense in on a rush and passed the puck to Garrett Ross, whose shot deflected off of the post and Flyers goaltender Brad Phillips before crossing the goal line.
Philadelphia responded in the second period with three goals from three different players - Tyler Brown, Blake Kessel and Thomas Hyka - to take a 3-1 lead into the second intermission. The second period also saw three fights as Dustin Stevenson, Reid Edmondson and Danick Paquette all squared off for the Caps.
Garrett Mitchell cut the Flyers' lead to 3-2 at 4:09 of the third period when he put a rebound from Dustin Stevenson past Michael Houser. Washington threatened throughout the third period after Mitchell's goal, but could not beat Houser again.
The loss gives the Caps a 2-3-0 record against the Flyers in rookie competition. Thursday's game was actually the lowest-scoring game in terms of combined score between the two teams as the Caps and Flyers combined for five goals. The previous lowest total was seven goals in 2008 and 2010.
Veterans will report to training camp tomorrow, but on-ice sessions open to the media and public begin at 9:15 a.m. Saturday morning at Kettler Capitals Iceplex in Arlington.