First of all, I've been thinking about what happens when the Phillies trade Marlon Byrd. Byrd's trade rumors have disappeared in the shadow of the Jimmy Rollins deal, but consider this epic list of fWAR for "OF" for the Phillies going back to 1900. Look at it.
Astute observers will note that the worst outfield the Phillies have had since 1900 (inclusive!) was in 1970. The 2013 Phillies were the second-worst out of 115 possible outfields. The 2014 Phillies experienced a dead cat bounce with a healthy Ben Revere and a decent Marlon Byrd, and they were only 108th worst. Getting rid of Tony Gwynn, Jr., will help, but yoinks. Domonic Brown and Revere effectively cancelled each other out last year, and I don't see much hope for anything different there. Losing Byrd from right and replacing him with a worse player puts things back into 2013 territory...or maybe beyond.
By way of comparison here, Lenny Dykstra posted an fWAR of 9.0 in 1990, which was more than 5 times the fWAR the 2014 Phillies outfield combined to produce. Years of big WAR numbers from the likes of Bobby Abreu, Shane Victorino, Jayson Werth, and even Hunter Pence, got us used to good outfields. Any of those players top few years easily topped the production from the entire Phillies outfield for 2013 and 2014 *combined*.
Keep in mind that the Phillies have had 14 teams with 100+ losses since 1900. Two of the worst outfields of the last 115 years for the Phillies were from the last 2 years. Those 100 loss teams may have lost for other reasons, but when your 100 loss bad team's outfield can "beat out" many other outfields from many other truly horrific teams, there is a serious problem. "But Chuck Klein!" you say. Yes, he helped crappy Phillies teams have decent outfields all on his own, but there were others.
The Phillies outfield of 2007 was the 10th best (14.2 fWAR) in the same period, and the decline from that period to the -1.5 of 2013 is nearly linear, and amazing to behold. It was caused by all the things we've beat to death around here: age, a changing cast of characters, and nothing to replenish the emptying cupboard, either from trades, signings, or internal development. All those toolsy draft picks just went to die in the minors.
What does 2015 hold in store? Ben Revere, Dom Brown, and probably no Marlon Byrd. Jeff Francoeur? Odubel Herrera?
It is possible (maybe with an injury to Revere) that the 1970 Phillies status as the worst Phillies outfield (with -2.2 fWAR) since 1970 is in jeopardy. It's not every year that you get to see history being made, folks. We have a chance this year.