I was recently watching an MLB Network documentary on the 1990 World Champion Cincinnati Reds. The major thing that anyone remembers about that team is The Nasty Boys, their incredible three-headed bullpen monster made up of Norm Charlton, Rob Dibble, and Randy Myers. Teams are trying to replicate that success, with the 2015 Royals and the 2016 Yankees being particularly notable. The documentary referred to the three pitchers' SO/9 numbers as the best evidence of their dominance (though it erred when it said all three had more than 10 strikeouts per nine as Charlton only had 6.8). I decided to use 9.0 SO/9 as a base line and find years in which the Red Sox had two or more relief pitchers with a higher number (using 50 innings pitched as a minimum). It is not perfect, not even close really, but it is a start.
1989
THE PITCHERS: Lee Smith (12.2 SO/9) and Rob Murphy (9.2 SO/9). #3 was Joe Price with 6.7.
Lee Smith was a monster. He was the closer in 1989 and was 6-1 with a 3.57 ERA, striking out 96 in 70.2 innings. He walked 33 for a 2.91 SO/BB ratio. He racked up 25 saves. His ERA was a little high for a closer but that SO/9 ratio was incredible.
Southpaw Rob Murphy was in his first year with the Red Sox after being acquired in a trade with the Reds that also included Nick Esasky. Boston gave up Todd Benzinger, which worked out well for Boston. Murphy was awesome in 1989 going 5-7 with a 2.74 ERA. He led the team in games pitched (74), and struck out 107 in 105 innings. He saved nine games.
2010
THE PITCHERS: Jonathan Papelbon (10.2 SO/9) and Daniel Bard (9.2 SO/9). #3 was Scott Atchison with 6.2.
In his prime, Papelbon was one of the most dominating closers in Red Sox history. At this point, he is the greatest closer in Red Sox history. 2010 was a bit of a down year for him, but he still managed to save 37 games, striking out 76 and walking 28 in 67 innings. Even in a down year he was striking out 10.2/9 innings.
Daniel Bard, on the other hand, was at his best in 2010. He saved three games and had a 1.93 ERA in 74.2 innings. He racked up 76 strikeouts and walked 30.
2011
THE PITCHERS: Jonathan Papelbon (12.2 SO/9), Matt Albers (9.5 SO/9), and Daniel Bard (9.1 SO/9). #4 was Dan Wheeler at 7.1.
Papelbon was back at the top of his game in 2011, though he did take the loss in the final game of the season that eliminated the Red Sox from making the postseason. He was 4-1 with a 2.94 ERA, striking out 87 and walking just 10 in 64.1 innings.
Bard, on the other hand, was starting his downward spiral. He still pitched well enough in 2011, finishing with a 3.33 ERA, but a 2-9 record. He struck out 74 and walked 24 in 73 innings for an impressive 3.08 SO/BB ratio, so that was not the problem. Bard would struggle greatly after 2011 though.
For the first time, Boston had three relievers with more than a strikeout an inning. Albers struck out 68 and walked 31 in 64.2 innings, but he had a 4-4 record and 4.73 ERA. He was not great, other than the strikeouts.
2013
THE PITCHERS: Koji Uehara (12.2 SO/9) and Junichi Tazawa (9.5 SO/9). Andrew Miller (14.1 SO/9), Andrew Bailey (12.2 SO/9), and Brandon Workman (10.2 SO/9) all did very well in shorter work.
The World Champs had a top-flight closer, having an amazing season. Uehara was 4-1 with a 1.09 ERA and 21 saves. He struck out 101 and walked just nine for an incredible 11.22 SO/BB ratio in just 74.1 innings. He won the ALCS MVP.
Tazawa was a very underrated member of the Red Sox bullpen for years. He was 5-4 with a 3.16 ERA in 68.1 innings. He racked up 72 strikeouts and walked just 12 for a 6.00 SO/BB ratio.
2014
THE PITCHERS: Same culprits as 2013. Koji Uehara (11.2 SO/9) and Junichi Tazawa (9.1 SO/9). Andrew Miller (14.7 SO/9) once again excelled, though in just 42.1 innings, and this was the season he was traded to Baltimore.
Not quite as impressive as 2013, but Koji was still 6-5 with 26 saves and a 2.52 ERA in 64.1 innings. He struck out 80 and walked just eight. His impeccable control was his biggest strength.
Tazawa had some better numbers in 2014, going 4-3 with a 2.86 ERA. He struck out 64 but walked 17 in 63 innings. His SO/BB ratio dropped to 3.00, which was still a pretty decent number.
2016
THE PITCHERS: Craig Kimbrel (14.1 SO/9), Matt Barnes (9.6 SO/9), and Robbie Ross Jr. (9.1 SO/9). Junichi Tazawa (9.8 SO/9), Koji Uehara (12.1 SO/9), Joe Kelly (10.8 SO/9), and Brad Ziegler (9.4 SO/9) just missed the innings cut-off.
Kimbrel's first season in Boston had its ups and downs, but he was still a strikeout machine, notching 83 in 53 innings. His SO/BB ratio was down to 2.77 and his other numbers were down somewhat as he had a 2-6 record and 3.40 ERA. He picked up 31 saves.
In his first full season in the Red Sox bullpen, Barnes put together a solid year. He had a 4.05 ERA mostly as a result of a few bad outings due to overwork. He struck out 71 and walked 31 in 66.2 innings. Barnes could get even better.
Ross has quietly been a very impressive member of the Red Sox bullpen as the primary lefty. He had a strong season that should get him some more notice in 2017 (I'm talking to you Topps, we need Robbie Ross cards). He was 3-2 with a 3.25 ERA, walking 23 and striking out 56 in 55.1 innings.
CONCLUSION
One team that just missed the cut that I was somewhat surprised by was the 1993 team. Four relievers had over 8.0 SO/9, but less than 9.0. That quartet was made up of closer Jeff Russell (8.7 in 46.2 innings), Greg Harris (8.3), Ken Ryan (8.8), and Tony Fossas (8.8 in 40 innings). That was a very underrated pen.
I personally remember the 2013 season very fondly, for obvious reasons. I did not even discuss Craig Breslow and Felix Doubront who also pitched well in relief. Injuries kept that pen from being even better. Bailey and Miller were both lost for the season early on. Of course, if Bailey had not been hurt, Boston may not have gotten the year it did from Uehara. The bullpen in 2013 was one of the team's strengths and a big reason why they won the World Series.
From a strikeout standpoint, the 2016 team was probably the most impressive. It is kind of amazing how many of these teams have come in the last five years. This is definitely becoming a primary focus in bullpens. The 2017 team could be the best yet. Barnes, Ross, and Kelly will all be back, with a better idea of what their roles will be. Kimbrel could have a bounceback season. And new setup man Tyler Thornburg had a 12.1 SO/9 ratio last season.