Throughout the Flyer's history, there have been some great pairings on defense. Chris Therien and Eric Desjardins were a steady, steady combo throughout the 90s. Mark Howe and Brad McCrimmon patroled the blue line together in the1980s. Joe and Jimmy Watson were essential parts of the Bully Era Flyers. Even more recently, Chris Pronger and Kimmo Timmonen formed a formidible pair for the Flyers.
However, one great pair is never enough. Try as he might, Pronger's heroics in the Stanley Cup run of 2010, where he played almost 30 minutes a game, is proof of that. You need at least five other defenders.