Shouldn't Will Middlebrooks be on this list? He was pretty darn good for two seasons before he just cratered. He's why they dealt Youkilis away.
While it's arguable that Cherington felt comfortable trading Youk because of Middlebrooks' performance to that point, that wasn't the reason he did it. Middlebrooks had been good prior to the Youk trade: 41 games, .326/.365/.583/.949, 9 HR. He also had a BABIP of .380 to that point.
Post-trade 2012 Middlebrooks: 34 games, .244/.277/.423/.700, 6 HR, .282 BABIP.
Post-2012 Middlebrooks: 272 games, .210/.256/.356/.611, 28 HR, .259 BABIP.
Conclusion, Middlebrooks never had even one good season. He had a good two months at the start and then it was downhill from there.