To be clear, when I started I was criticizing soxhop's interpretation of the tweet. The discussion expanded talking about the hypothetical.
That said, I am on record here and maintain my opinion that Farrell is not the guy for developing young talent. When viewed in this lens, the somewhat ambiguous quotes take on a bit more focused meaning. I hope he proves me wrong.
I am struggling to find evidence that Farrell cannot develop young talent. This may be a thread in and of iteslf, but looking at the young position players that have come up through the system while Farrell was here:
Middlebrooks: Struggled under Farrell. But has struggled in San Diego as well. He just may not be very good at the plate.
Iglesias: Hit 0.330 under Farrell.
Bogaerts: Had a breakout year last year, and it started while Farrell was still the manager (a respectable 0.750 OPS in the 1st half of 2015). Aside from his ill timed slump in 2014, that happened to coincide with a position switch, there's nothing to indicate that Farrell has done anything wrong with Xander. And Xander was only 21 in 2014.
Vazquez: Performed as expected, if not better than expected, offensively in 200 plate appearances in 2014.
Brock Holt: 0.711 OPS in 2014, selected to All Star Team in 2015 as the Sox sole representative.
Betts: 0.812 OPS in 2014, 0.792 in first half of 2015.
Swihart: He also had his first major league at bats under Farrell, after all of 150 plate appearances spread over 2 seasons in AAA, and he seemed to be set up well by the time he had his breakout in August, which was fueled in part by a 0.477 BABIP.
Castillo: Barely broke 100 plate appearances under Farrell. He's definitely a unique case, so I'm not sure I would attribute Castillo's performance up until now to anything Farrell did or did not do. And his BABIP was 0.421 during his August breakout.
JBJ: His struggles under Farrell, and his breakout August, have been well documented elsewhere.
So really the only two true prospect "failures" under Farrell were Middlebrooks (who just isn't very good hitter anyway) and JBJ, who benefited mightily from a 0.450 BABIP last August. I'd say every other young player performed as expected or better under Farrell. And a lot of the improvement of the Sox younger players under Lovullo was indeed BABIP related; JBJ, Castillo, Swihart, Betts, Bogaerts all benefited from the BABIP gods in August and September. Bottom line is that Castillo and Bradley are still big question marks offensively.
The real issue with the team the past 2 seasons is that the vets brought in in 2013 all declined, markedly in some cases. And the vets brought in to replace those vets (Panda, Ramirez, Porcello, Miley) haven't been the answer. Sometimes it is the players, not the manager.