The Red Sox are a good offensive team. They scored 876 runs this season, 25 more than any other team. It’s not surprising—or at least not shocking, given their playoff opponents—that they managed to get to the World Series, as they had an offense that featured a potential MVP in addition to a near–Triple Crown winner.

However, their defense leaves much to be desired. Of all the teams to make the World Series since 2003—when Sports Info Solutions started reporting Defensive Runs Saved (DRS)—the 2018 Red Sox team has the third-fewest DRS at minus-26 (tied with the 2004 Red Sox, coincidentally enough). The infield has been the primary force behind that total, as Red Sox infielders combined to cost the team 60 runs this season, worst in the majors.

With the news that Mookie Betts may see time at second base to squeeze J.D. Martinez into the lineup in games at Dodger Stadium, an already-shaky defense could become even more concerning. Betts is the best fielder (at least compared to an average player at his position) on the Red Sox, saving 20 runs this season to lead right fielders.

We can’t be sure exactly how the Betts situation will play out, but, being fairly confident about who will be manning the other positions, it’s worth taking a look at some of the more interesting defensive storylines between the two teams to find where one might have an edge over the other.

Catcher

Both teams were at or near the top of their respective leagues in terms of runs saved by their catchers. Sandy Leon saved 12 runs this season, which was tied for the second-highest total at the position. Christian Vazquez, though, was merely average, and has shared time relatively evenly with Leon.

The Dodgers have two catchers who excelled on defense: Yasmani Grandal and Austin Barnes. Both saved at least nine runs this season, which ranked them top 10 at the position. Based on how much mixing and matching both teams have employed throughout the season, having two solid defensive catchers figures to pay off for the Dodgers.

Shortstop

Manny Machado’s transition back to shortstop was a rocky one, as he cost his teams a combined 13 runs at the position, third-worst in baseball (he saved the Dodgers three runs at third base in about 150 innings). He’s shown some improvement, though. Through July 14—or just about the first half of the season—Machado had cost the Orioles 20 runs at shortstop. Since then, he’s worked his way back up to his final total, saving seven runs over the last two and a half months of the season.

Given that, you’d think that the Red Sox have the advantage defensively. But their shortstop, Xander Bogaerts, cost the most runs of any shortstop in baseball (19). They struggled in opposite areas (Bogaerts was 36 plays below average on plays in the third base–shortstop hole, while Machado was minus-13 on plays up the middle), but Machado has to be given the slight edge here, especially given his improvements as the season wore on.

Center Field

Many will say that Jackie Bradley Jr. is the best defensive center fielder in baseball, or if not the best, then at least in the conversation. DRS has largely agreed with that notion in the past, with Bradley finishing no worse than seventh among center fielders in his qualifying seasons between 2014 and 2017 and saving more runs (39) than all but five other center fielders during that timeframe.

This year, though, Bradley has cost the Red Sox two runs, in large part due to balls that he’s allowed to fall behind him. Despite making three more plays than the average center fielder on balls hit shallow, he’s been five plays worse on balls hit deep, likely due to his playing nine feet shallower on average compared to last year. Those balls lead to extra-base hits, which in turn hurt Bradley Jr. more than balls in front of him help.

Meanwhile, Cody Bellinger has displayed his athleticism for the Dodgers, saving six runs in center field in his first real season there. That’s not to say Bellinger is decidedly a better fielder than Bradley Jr., but the Red Sox may not have as clear of an advantage at the position as some may think.

Right Field

If Mookie Betts remains stationed in right field, the Red Sox have the clear advantage—not just over the Dodgers, but over anyone. Betts has won two straight Fielding Bible Awards, which recognize the best fielder in baseball at each position, and has saved 83 runs since taking over the full-time role in 2016, 22 more than the next-best outfielder (Kevin Kiermaier).

Of course, if J.D. Martinez sees action there, it’s an entirely different story. For his career, Martinez has cost his teams 31 runs in right field. Admittedly, that’s largely affected by his 2016 season where he cost the Tigers 22 runs. Even ignoring that season, he’s still been average defensively at best.

For the Dodgers, Yasiel Puig certainly holds his own in right field, at least tying for the ninth-most runs saved at the position each of the last three years. His recent contributions to the team have come from his bat, but he’s more than capable of making a defensive play when he’s called upon.