Boston's starting pitching:
Porcello: 4.1 ip, 6 h, 5 r, 5 er, 0 bb, 6 k
Price: 3.1 ip, 6 h, 5 r, 5 er, 2 bb, 3 k
Buchholz: 4.0 ip, 6 h, 2 r, 2 er, 1 bb, 4 k
TOTAL: 11.2 ip, 18 h, 12 r, 12 er, 3 bb, 13 k, 9.26 era, 1.80 whip, 10.0 k/9
That's problem number one.
Problem number two - the offense.
7 runs, 21 hits, batted .214/.278/.378/.655
When two huge components of your team is woefully underperforming (for whatever reason), it's going to be tough to win.
The Sox went 1-8 in their last 9 games of the season, including postseason. During that time, their starting pitching did this:
Last 6 games: 33.0 ip, 32 h, 15 r, 15 er, 15 bb, 33 k, 4.09 era, 1.42 whip, 9.0 k/9
Postseason: 11.2 ip, 18 h, 12 r, 12 er, 3 bb, 13 k, 9.26 era, 1.80 whip, 10.0 k/9
TOTAL: 44.2 ip, 50 h, 27 r, 27 er, 18 bb, 46 k, 5.44 era, 1.52 whip, 9.3 k/9
The starting pitching was acceptable down the stretch but putrid during the playoffs.
Meanwhile, their offense did this:
Last 6 games: 191 ab, 17 r, 38 h, 24 bb, 7 2b, 4 hr, .199/.288/.298/.586
Postseason: 98 ab, 7 r, 21 h, 8 bb, 6 2b, 3 hr, .214/.278/.378/.655
TOTAL: 289 ab, 24 r, 59 h, 32 bb, 13 2b, 7 hr, .204/.283/.322/.605
The offense was terrible the entire last 9 games of the season/postseason.