Red Sox's Margin of Error Exists Solely Because of Their Elite Defense

The Boston Red Sox have the most consistent bullpen in the major leagues this season, leading with fWAR (6.1) and xFIP (3.76). The starters have also done a dominant job, accumulating the second-best fWAR (12.3) in the American League. But when we talk about how they are dominating the opposition and controlling the game, we cannot forget the enormous contribution of the defense.

In that equation, the outfielders have taken the team to another level. One of the reasons why Boston did not completely sink during their bad stretch in the first half of the season was its elite outfield defense. The Red Sox lead the majors with +49 DRS and 5.0 ARM (arm value). They also lead the league with 31 assists, 26 of them recorded by Ceddanne Rafaela (center fielder), Wilyer Abreu (right fielder), and Jarren Duran (left fielder).

The only comparable trio in the entire league is that of the Chicago Cubs’ outfielders, who have the advantage because of the incomprehensible value Pete Crow-Armstrong provides (seriously, he's comically overpowered in center field). Let’s see how both groups compare this year by adding their DRS, OAA, and FRV values.

The Red Sox dominate in DRS, but the Cubs make up ground in OAA and FRV. The difference, to a large extent, is PCA. Abreu and Rafaela surpass the Cubs' star in DRS, and this year Seiya Suzuki has also contributed important defensive value.

The comparison between Duran and Ian Happ looks interesting in these combined metrics. Happ has won four Gold Gloves, but Duran surprised me a little by surpassing him in OAA. That Happ remains a great candidate to win the Gold Glove again in the National League for the fifth consecutive year is a pretty strong endorsement of the gains Duran has made on defense this season.

The defensive consistency of Abreu and Rafaela is fascinating. Abreu is on his way to collecting his third consecutive Gold Glove, while Rafaela is also the favorite to get his second.

Were it not for PCA, Rafaela would be the most complete center fielder defensively in all of baseball this year. Among the center fielders that we can evaluate with FanGraphs metrics, Rafaela appears second in defensive value with 10.9, only behind PCA (21.7). Abreu leads the league with 24 DRS, but if we extend the filter to the last two seasons, Rafaela ties him with 39. Both are tied with Steven Kwan. PCA (29 DRS) fell a little farther behind, but leads both other main categories, with 43 OAA and 45 FRV.

I do want to revisit Duran as well. In left field, he has -0.3 defense value, but +3 DRS with positive grades in arm value and range. His impact does not come close to that of Rafaela or Abreu, but with Roman Anthony out due to injury for a good part of the season, Duran has been a complement that continues to strengthen Boston’s defensive formula. The numbers also show the advantage that the Red Sox are getting from the defense against several of their main American League contenders.

Defensive Rankings - 2026

The defense that comes closest to the Red Sox’s level is that of the Rays, although the former maintains a clear advantage. Among their main contenders, the Yankees (-6), Orioles (-9), and Tigers (-10) appear far below. That is a difference we cannot forget when the pressure is even greater in the final stretch of the season. And I still feel that these metrics do not tell the whole story of what a defense can generate when it operates as efficiently as this one. For us, it is much easier to have a judgment about a quality at-bat or a pitch that did not meet expectations at the key moment. On the other hand, you never really know how many opportunities a defensive error can give up.

The Red Sox are not playing with the same margin for error as a year ago, but thanks to the strength of their defense, they do have a distinct advantage over every single American League contemporary.