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This is not in any way an attack on Nick Foles. Foles is an excellent player and has had an impressive preseason (except for his last game). Foles will be an excellent backup to Michael Vick.
However, Foles' best value is not as a second-string quarterback. His best value is in the form of trade bait.
Foles is just coming off a quarterback battle that he lost because his opponent, Vick, significantly stepped up his game, rather than as the result of poor play from Foles. Following impressive preseason performances, his value will never be higher than it was when Vick was named the starter.
Plenty of NFL franchises are desperate for a starting-caliber quarterback. When teams like the Oakland Raiders are resorting to an undeveloped Terrelle Pryor, Kelly made a critical error when not capitalizing on an opportunity to get great value for the backup quarterback.
While Foles can always be traded next offseason, by then, his value may be significantly lower. It's expected to be an excellent quarterback class, containing the likes of Terry Bridgewater, Tajh Boyd, Johnny Manziel, and AJ McCarron just to name a few.
Next season, many NFL franchises will turn to the draft to solve their quarterback woes. The Eagles would be lucky to get as high as a fifth-round pick for Foles and would likely have to settle for an even lower draft pick.
Follow Yueh Ho on Twitter @YuehHo.