One thing Boston has not been able to do the last few years is field a championship-caliber defensive team. There are many different reasons for that, having to do with the construction of the roster, injuries, or even just players not doing as well as they were expected to, but it's been tough to claim the Red Sox have been a top fielding club as of late regardless of the why.
In 2007, the last time they won the World Series, the Red Sox had the second-best defense in the American League (and the third in the majors) according to Defensive Efficiency. Defensive Efficiency tracks the percentage of balls in play turned into outs on a team level, and therefore is a practical way of comparing team defense -- both a hit and an error are a non-out, and therefore count against the fielder, unlike an overly simple metric like Fielding Percentage. Booted a ball? That's a non-out. Can't get to your left on a groundball? That's a non-out, too, and the team's rating is punished for that as well.
The Red Sox didn't have that problem often in 2007, as they converted 71.6 percent of balls in play into outs. The average batting average on balls in play in the majors is around .300, so converting nearly 72 percent of balls in play into outs means that particular team was allowing a .280 team BABIP. Simple, clean, and an easy way to track how well fielders are converting non-strikeouts into outs for their pitchers.
They haven't been that efficient since, though they came close in 2008. In 2009, the Red Sox had a terrible defensive team that ranked 29th in the majors, converting just 69.1 percent of balls in play into outs -- that's a BABIP allowed of about .310. Having Jason Bay in left field hurt -- and that's coming from the same team that brought you The Adventures of Manny Ramirez in left -- and Jacoby Ellsbury was very clearly still learning how to handle center field at that stage, too. Kevin Youkilis, Dustin Pedroia, and J.D. Drew were all positive defenders, but Mike Lowell was hobbled by his hip and cost the team dearly, Nick Green and Julio Lugo did their best to destroy the chance of getting any production out of shortstop for most of the year, and the Jason Varitek/Victor Martinez combination behind the plate ranks up there with some of the worst in recent memory in terms of defensive prowess -- Varitek threw out just 13 percent of opposing baserunners, and Martinez, just two years later, is the primary DH in Detroit for a reason. The fact this team won 95 games is honestly nothing short of a miracle.
Theo Epstein and Co. were aware of this, so the 2010 team focused on defense, bringing in Mike Cameron to man center field, Marco Scutaro to play shortstop, and shifting Ellsbury to left, where his routes would work better and his speed could be utilized without having to resort to last-minute dives. Adrian Beltre, aka The Greatest Defensive Third Baseman In The League, took over for Mike Lowell on a one-year deal, too, giving Boston a formidable defensive unit in both the infield and outfield. Behind the plate was still an issue, but that Martinez guy knew a thing or two about hitting, and was expected to more than make up for whatever throws he couldn't make or passed balls he allowed.
That was in theory, anyways. Cameron was hurt early, and ran the outfield like a man whose stomach was torn asunder... most likely because it was. Ellsbury barely played due to an injury you can read about in the award-winning novela, "Ode To A Bruised Rib Cage, Or, How I Figured Out My Ribs Were Broken After Weeks On Painkillers And Even More Outfield Dives." Scutaro dealt with minor injury after minor injury, eventually being forced to second base because he could still make those throws while hurt. Pedroia and Youkilis both missed significant time, keeping their gloves off of the field. But hey, at least Beltre was everything we ever wanted out of a third baseman on both sides of the ball.
Unsurprisingly, the 2010 team did not regain the defensive glory of the 2007 squad, though, even with the defensively-average Darnell McDonald in center, the offensively-oriented Bill Hall at second, and DH-With-A-Glove Daniel Nava in left, they managed to improve on 2009's abysmal effort.
Boston lost Beltre to free agency, but didn't sit back and wait for another 2009 to happen. They traded for Adrian Gonzalez, one of the few first basemen in the league who could brag about being both a better hitter and defender than Youkilis. They shifted Youkilis to this old position of third, where he was no longer expected to be a high-quality defender, but where his bat would more than make up for that difference. Cameron was made a fourth outfielder so that the team could bring in the top defensive left fielder in the game, Carl Crawford. Pedroia was back to play second for the full year, meaning no more Hall or one-armed Scutaro at the keystone, and the team handed the catcher job to Varitek and Jarrod Saltalamacchia, a combo that would not hit as well as the departed Martinez, but would most assuredly play better defense.
This revamped lineup is not only killing it on offense, but has also played well on the field. Boston is fourth in the majors and third in the American League in Defensive Efficiency, converting 72.3 percent of balls in play into outs. This defense will help out John Lackey as he struggles to regain his old form -- if he ever can -- and has been able to assist Tim Wakefield and Alfredo Aceves as they fill in for starters that were (at least in theory, were supposed to be) more capable. Andrew Miller, even if his walk rates don't look as good as they did towards the end of his Pawtucket stay, should get a boost from a defense of this quality. And Jon Lester, Clay Buchholz, and Josh Beckett, while certainly not needing as much help as your average starter, certainly won't turn down the assist for those times they don't get the out themselves. Especially Buchholz, whose game is defined by his ability to induce weaker contact than your average hurler.
Defense was the key in 2007, and while the Red Sox have almost approached those heights since, they have been all over the place in terms of quality, and unable to fully reach them. This year may be different, and, given the wonderful combined hitting ability of the fielders in question, realize that this is a special -- and positive -- thing.