Boston has made a lot of moves this offseason, but the biggest additions to the team may simply come from the improved performance of the Red Sox starting rotation.
The Sox are hoping that improvement starts with the hiring of Farrell this offseason.
Last season, the Red Sox pitching staff had a 4.70 ERA, which was the fourth-worst in baseball.
In 2010, Farrell's last season as the Red Sox pitching coach, the team's ERA was 4.20, a half-run better.
When the Red Sox fired manager Bobby Valentine this past October, they immediately looked at Farrell as their clear first choice for the job.
Farrell was under contract at the time with the Toronto Blue Jays, something that took some time behind the scenes for the Sox and Jays to resolve.
The Sox obviously viewed Farrell as someone who could control the clubhouse and impact on the pitching staff, specifically the starting rotation, based on his history.
Jon Lester in 2010: 19-9 record with a 3.25 ERA, 1.20 WHIP and 9.7 strikeouts per nine innings.
Will John Farrell have a big impact on the Sox' starters?
Jon Lester since: 24-23 record with 4.17 ERA, 1.32 WHIP and 7.88 strikeouts per nine innings.
Clay Buchholz in 2010: 17-7 record with a 2.33 ERA, 1.20 WHIP and 6.2 strikeouts per nine innings.
Clay Buchholz since: 17-11 record with a 4.24 ERA, 1.32 WHIP and 6.25 strikeouts per nine innings.
If the 29-year-old Jon Lester and the 28-year-old Clay Buchholz can regain their 2010 forms under Farrell, the Sox immediately transform from a 69-win team to something far greater.
It's no coincidence that the Sox' first addition under Farrell this offseason was catcher David Ross from the Atlanta Braves. Ross will hopefully fill the role of veteran leader since the retirement of captain Jason Varitek.
A strong offense will allow the Sox to take advantage of their extremely deep bullpen, aided by the additions of Koji Uehara and closer Joel Hanrahan.
But, make no mistake, the Red Sox will only go as far as their starting pitching takes them in 2013.