This is why the Red Sox are so good so far

Last year's Red Sox lineup was one of baseball's weakest in the power department, finishing last in the American League in home runs and next to last in slugging percentage. You knew that, because it was talked about endlessly all offseason, particularly regarding their months-long pursuit of slugger J.D. Martinez.
Despite the lack of power, it was always clear this lineup was going to be better. Way back in February, we noted that Boston projected to be baseball's third-best offense, and it wasn't just about Martinez. It was because it was all but a guarantee that Mookie Betts and Xander Bogaerts would improve from down years after playing through hand injuries, and because new manager Alex Cora's insistence that he wanted the lineup to be more aggressive seemed like a step in the right direction.
Well, the Red Sox have been better, but at least early on, we may have undersold them by suggesting they could be the "third-best" offense. They're the best, by a lot, and a big part of that is because they're pulling off a trick that last year's World Series champions in Houston managed to do.
Boston has baseball's highest slugging percentage, at .485. It has baseball's lowest strikeout percentage, at 16.6 percent. The Red Sox are hitting the ball a lot, and destroying the balls they connect with. It's how you end up with baseball's highest runs-per-game, at 6.4. It's the perfect combination.

That's impressive on a team basis, but also look at what's happened on an individual basis. Ten batters have taken at least 30 plate appearances for Boston in both 2017 and '18. Every single one has had at least a small decrease in strikeout rate.

Now, let's be clear about one thing: While contact is good, simply making contact does not by itself make you a good offense. Last year, two of the five best contact teams were the punchless Royals and Giants, who were below-average offenses. When the 2015 Royals famously rode a contact-heavy approach to a title, the next two best contact teams were the A's and the Braves, who lost 94 and 95 games, respectively. It's good, but there has to be more.
Aside from the fact that it's still early in the season, how exactly have the Red Sox pulled this off? Let's check out three possibilities.
New faces
Because of the extended courtship of Martinez, and because he out-slugged everyone in baseball last season -- even Aaron Judge and Giancarlo Stanton -- it's tempting to simply point to the fact that there's a new elite bat in the lineup. Martinez is fantastic, and he's hitting .313/.343/.578, while Boston is no longer giving time to Chris Young (.235/.322/.387 last year) or Pablo Sandoval (.212/.269/.354), so there's some truth to that. Martinez is wonderful. He'd help any lineup.
That said, Martinez has hit only 70 times so far. Pretty much everyone else is the same, other than the fact last year's rookie sensation at third base, Rafael Devers, is around from day one this year. They've helped, but it's not just about new talent.

Better health
Since much of the improvement is simply about existing guys performing better, this is a natural place to look, and there's some pretty obvious stories here.
We knew that Bogaerts' second-half slide was in some way related to being hit by a pitch on July 6, as he hit .308/.363/.455 before that and just .232/.321/.340 after, and he admitted as much during Spring Training.
"To a point, I do regret [playing through pain], but it's over with," Bogaerts told MLB.com in February. "We were in the heat of things, we were pushing for the playoffs. You don't want to be the guy on the bench not being able to help your team to win. You learn, and I definitely did."
Bogaerts was off to a smoking start (.368/.400/.711) this season before injuring his ankle.
We knew, also, that Betts playing through a thumb injury hampered his performance last season. He went from .280/.356/.490 through the end of June, and just .248/.332/.427 after that. 
"It's been going on for a couple months, but I was able to just kind of play through it," Betts said when he was forced to come out of a game against the Rays in September due to a thumb contusion. So far in 2018, he's been baseball's best hitter.
Finally, Hanley Ramirez, who struggled through most of 2017, underwent left shoulder surgery in October. After hitting .242/.320/.429 last year, he's slugging .322/.369/.542 so far.

A new approach
This is the one that got the most press, simply due to Cora talking about being more aggressive. There's something to this, though this is hardly the whole story.
Last year, Boston hitters went after 57 percent of pitches in the zone or on the edges. That was 30th in baseball. This year, that number is up to 63 percent. That's the most in baseball. As you'd imagine, that's the largest jump in baseball.
So yes, there's something to be said for "swinging at strikes," which the Red Sox now are -- especially because they have a .318 average and a .550 slugging on those pitches, each the best in baseball. It's not just about swinging either, it's about swinging earlier. For the past decade, Boston was always in the bottom three in baseball in swinging at in-zone strikes early in the count (0-0, 0-1, 1-0). This year, the Red Sox have done that the second most. As a result, they've found themselves in the fourth-fewest two-strike counts in the game. It's hard to strike out when you never see two strikes.
But there's more to it than just that. Betts, for example, has done more than just be aggressive, he's changed the way he's hitting entirely. After spending the past three years hitting grounders between 38 percent and 41 percent of the time, that's dropped all the way to 26 percent -- while his pull percentage has jumped from his career mark of 41 percent to 57 percent.
You can see it in the outcomes, too. Only two teams have a higher hard-hit percentage than Boston's 42.1 percent. Only four teams have a lower ground-ball percentage than the Red Sox's 41.7 percent. No one, as we said, strikes out less. This is essentially what the perfect offense is supposed to look like.
Now, Betts won't hit like this all year, most likely. Bogaerts can't slug .711 all season. Then again, Jackie Bradley Jr. hasn't done much yet (.228/.313/.351). Dustin Pedroia hasn't stepped on the field yet. Only two teams in baseball have gotten less offense from their catchers. As some fall back, others may step up.
We saw the Astros doing this last year, paired with a very good pitching staff. The Red Sox are doing it this year, paired with a very good pitching staff. You don't get off to a 15-2 start by accident.