In today’s MLB, bullpens are characterized by relievers who can come into the game with
overpowering fastballs. According to, the average velocity of a big league
fastball has risen from 91.1 mph in 2007 to 92.9 mph last season, and that trend is even
more evident in major league bullpens. During that same time period (and partially as a
result of this league-wide velocity uptick), strikeout rates across baseball have also
increased, growing from 17.1% in 2007 to 19.9% in 2013.

Last year, in other words, hitters struck out in one out of every five of their plate
appearances. Relievers showed an even greater ability to generate whiffs, posting a
21.7% strikeout rate against opposing hitters.

In 2013, the Red Sox bullpen fell right in line with this trend, striking out batters at a
23.3% rate. But unlike their fellow bullpen mates across baseball, Red Sox relievers didn’t
have quite the same propensity for lighting up radar guns, a reality that looks likely to
continue this season.

Photo by Kelly O'Connor of

Photo by Kelly O’Connor of

Indeed, the Red Sox bullpen is instead populated by pitchers who are known better for their control and command than their big fastballs and overwhelming stuff. When Koji Uehara entered our hearts last summer, it was with a fastball he could place wherever he wanted and a near-unhittable splitter, not some high-90s four-seamer that is difficult to catch up with.

The same goes for Junichi Tazawa and Craig Breslow, who held down the set-up role for Boston in 2013, but did so with finesse and command rather than the type of elevated velocity that has come to dominate major league bullpens. Uehara and Breslow’s fastballs both clocked in below 90 mph on average, while Tazawa’s generally sat at 93.5 mph, according to Brooks Baseball, just above the MLB average for relievers.

That trend looks likely to continue in 2014, with Uehara, Tazawa, and Breslow all back, and the Red Sox’s addition of Edward Mujica on a two-year, $9.5 million contract this offseason. Like his new bullpen mates, Mujica relies on changing speeds and sharp control to get hitters out, an approach he used to great results with the Cardinals last year.

The 29-year-old Mujica finished with a 2.78 ERA and struck out more than nine times as
many batters as he walked for the Cardinals, saving 37 games in 64.2 innings. His
numbers were eerily reminiscent of Uehara’s, with the two pitchers placing first and
second in strikeout-to-walk ratio among all pitchers (min. 50 IP) last season. Between the
two of them, Uehara and Mujica walked just 14 batters in the 2013 campaign.

The similarities between Uehara and Mujica don’t end there, however. Both pitchers rely
on dominant splitters to attack opposing hitters and generate whiffs. Uehara threw his
renowned splitter 48.4% of the time last season, and Mujica threw his even more, turning
to the offering on 56.3% of all his pitches. As the zone charts below show, the two right-
handers often buried their splitter down and below the strike zone, getting hitters to
chase the pitch as it dropped upon reaching the plate.

strike-zone (1)


These next charts show the opposition’s batting average against versus the splitter for
both pitchers. As you can tell, hitters didn’t have much success against either Uehara or
Mujica’s splitters when they spotted them low in the zone (which was more often than not
for both pitchers).

strike-zone (2)

strike-zone (3)

With the addition of Mujica and fellow right-hander Burke Badenhop, the Red Sox bullpen
only looks stronger for 2014. The potential for injury is always a concern (after all, both
Joel Hanrahan and Andrew Bailey had to get hurt for Uehara to assume the closer role
last season), but with Mujica and Badenhop in the fold and Andrew Miller returning from
injury, the Red Sox will have a strong stable of relievers to call on when Opening Day
arrives. Miller is perhaps the team’s only pitcher who fits the more common reliever mold,
as someone who can pump his fastball into the mid-90s.

That the Red Sox have shown little regard for pursuing high-velocity relievers makes one
wonder if they are exploiting the way relief pitchers are perceived and valued on the open
market. After all, they were able to lock up Mujica for just over $4.5 million per season
through 2015 when pitchers like Brian Wilson and Boone Logan (neither of whom have
matched Mujica’s recent track record) will make much more in the year ahead.

Last offseason, Boston was able to tie up Uehara on the cheap even though he had been
one of the more consistent relievers in baseball over the three seasons prior. Such
shrewd spending has allowed the Red Sox to build an effective bullpen without committing
much of their payroll to relief pitching. And although Red Sox relievers might not light up
the radar gun like their brethren across the league, that hasn’t diminished their results in
any way.