The biggest thing which none of us can put our finger on is the volatility from year to year during the Farrell era:
How do you assess Farrell's roll in:
Rick Porcello going bleh, to Cy Young to meh.
Or Hanley going from awful, to solid, to meh at best.
Or with Chris Young going from the perfect platoon bat to liability.
Or Sandoval being the worst player in baseball after being a solid regular
And good Buchholz vs. bad Buchholz
Or Victorino, Napoli and Peavey dying after the 2013 season
Or Xander's Jekyl and Hyde
Or the whiffs on catcher development and 5 non-aces
Or Pedey's health issues
Or being the best baserunning team in baseball, to whatever this years version is with better personnel.
Or Papi saving his best for last.
Most importantly going first, to two years in last, to first, to underachieving Golden State Warriors.
Let's give this a shot:
Porcello - 2016 was his career year. It happens.
Hanley - Physical issues drive his results
Young - Blah hitter as position player, fine hitter as PH, but strangely struggles in DH role?
Buchholz - Struggles may have started with a physical issue where he faced a dilemma: pitch effectively and aggravate his neck/shoulder problem, or change his motion to avoid irritation and pitch less effectively.
Victorino - Arrived as a ticking time bomb - Pete Reiser v. 2.0 - and burned up his remaining fuse.
Napoli - Not really dead in 2014
Peavey - no idea on him
Bogaerts - Worrisome Aug/Sept in 2016, fatigue cited as a factor but seemed to give away too many ABs for his talent level
Catcher Development - Historically an organizational strength, no idea
Pitcher Development - Historically not an organizational strength, no news
Pedroia - What Artis Gilmore told Larry Bird
More aggressive baserunning - Right idea for 2017 club's offense, but not great execution
Papi -
sui generis
First to Last to First - If you can't finish first... Organizational philosophy was to strip-mine struggling club for future assets, but not great execution.
OK, you can link Ferrell to Young {stop putting him at DH}, and some portion of the blame pie for catcher development {role in Swihart saga?}, baserunning, and last-place finishes. You fire a manager who is one game out of 1st place, though, and the only replacements who will take the job will likely be desperate candidates such as BobbyV.