The Eagles have plenty of practice at facing top WR duos, results are a mixed bag
Calvin Johnson and Kris Durham, Lions
Jordy Nelson and James Jones, Packers
Victor Cruz and Hakeem Nicks, Giants
Larry Fitzgerald and Michael Floyd, Cardinals
Dez Bryant and Terrance Williams, Cowboys
Vincent Jackson and Tim Wright, Buccaneers
Pierre Garcon and Santana Moss, Redskins
Greg Jennings and Jerome Simpson, Vikings
They would get failing grades against the Broncos, Chargers, Chiefs, Buccaneers, and Vikings. Among the teams against whom they failed (based on my highly scientific pass-fail system), they went 1-4.
The Eagles' secondary hasn't completely shut anyone down this season, although they have faced some very good passing attacks. They have, however, often been "good enough." The Eagles need to just be "good enough" against the Bears' WR duo, which will be difficult. As long as they don't let Marshall and Jeffery run amok, I like their chances.