The Red Sox are tied with the Orioles for first place in the American League East after a 6-4 win in Boston on Wednesday. There's no shortage of reasons why Boston is succeeding -- from David Ortiz's record-setting pace to breakout years from Steven Wright, Xander Bogaerts and others -- but quietly, they've become the most efficient basestealing team in baseball. Just look at the top of the list of individual basestealers.
Most efficient basestealers, 2016 (minimum five steal attempts)
1. Mookie Betts, 100 percent (11-for-11)
2. Jackie Bradley, Jr., 100 percent (5-for-5)
3. Jose Altuve, 95 percent (18-for-19)
Two Red Sox at the top! Bradley and Betts are a combined 16-for-16 on steal attempts this year. Interesting! Bradley has still never been thrown out on a steal attempt in his Major League career, and he's now eight successful steals away from tying the all-time record of consecutive successes to begin a career, which is 26, set by Oakland's Mitchell Page in 1977. And then Betts might just be the best all-around baserunner in the game.
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So those two have been perfect at stealing bases, but as I scrolled down the list of basestealing efficiency, something caught my eye. In 11th place is Hanley Ramirez, who is 5-for-6. Bogaerts is four spots behind him, at 9-for-11. Two spots behind Bogaerts is Dustin Pedroia, at 4-for-5.
It's the whole team! But is it really the whole team? I made a new spreadsheet of team basestealing efficiency. I think this plot is pretty fun:

No one is even close to Boston's place on the X-axis. The next-most efficient team clocks in barely above 80 percent. In terms of efficiency, the gap between the Red Sox and second place is the same as the gap between second and 13th. The success rate would likely be lower if they ran more often, but they've still attempted an above-average rate of steals, and due to their efficiency, they've extracted significantly more value from their steal attempts than any other team in the league, despite having stolen 11 fewer than the league leader.
I wondered where this rate of efficiency might rank historically, so I grabbed stolen base attempts and successes for every team since 1961. The table:

We're more than one-third of the way through the season, and the Red Sox are running the highest stolen-base success rate the modern era has ever seen. Also, you'll note the 2013 Red Sox checked in at a fairly historic rate. Since the beginning of that '13 season, the Red Sox have been baseball's most efficient basestealing team (79.7 percent success rate). This year, they've just ramped it up.
When I wrote the Bradley post in the offseason, I included a John Farrell quote from 2014, when he cited the importance of quality over quantity:
"I think we always look at it as opportunistic," Farrell said. "We had a high success rate -- and success rate is probably the No. 1 thing. Do we have a 50-plus-stolen-base guy? No. But can we take advantage of some situations with an average-running-speed type of player? Well, we've proven that.
"The beauty of it all is that if a guy hasn't been a basestealing threat in his career, he knows he may be put in motion at times because of the homework our entire staff does. So it comes down to success rate."
Maybe the most interesting thing about this is that the Red Sox don't have a Billy Hamilton or a Dee Gordon or a Jonathan Villar. Those late 2000s Phillies teams that populate the table above had a couple true burners -- Jimmy Rollins and Shane Victorino were perennial 40-steal candidates. This team has got Bradley, who was never much of a basestealer in the Minors. Bogaerts was never anything of a basestealer in the Minors. Pedroia has always had success in the past, but he wouldn't be mistaken for a burner. Maybe the planets have just aligned this year, but then there's 2013, too, and it sure seems like maybe the Red Sox know how to get the most out of their stolen base attempts.

Going back to that Bradley post one more time, I looked at the batteries against which he'd attempted steals, and found some evidence to suggest that perhaps he was choosing the batteries against which he'd recorded his attempts very carefully. In other words, the distribution of his steal attempts was more heavily weighted toward pitchers who were slow to the plate and catchers with weak arms than the average basestealer. Only going when he felt he had an edge.
The trend seems to have continued this year -- he has twice stolen against a Russell Martin battery, and Martin has been dreadful against the run game this year, potentially due to the neck injury that has lingered for most of the season. Another came against a George Kontos / Trevor Brown battery, both of whom score below-average marks by Baseball Prospectus' Swipe Rate Above Average model. Same with the Ivan Nova / Austin Romine battery. Bradley continues to prey on weak opponent batteries.
A perusal of Bogaerts' stolen-base log reveals similar tendencies. Two against Ubaldo Jimenez, the easiest pitcher to steal against in 2015. Two more with Tyler Flowers behind the dish, one of the most exploitable catchers in baseball the past couple years. He's also had steals against Michael Pineda and Julio Teheran -- both impressive feats -- but a cursory glance of his steals shows more weak batteries than strong.
Of course, all teams are aiming to take advantage of weak batteries -- it's not like the Red Sox are the first to think of this -- but my gut tells me what Farrell's quote from 2014 seems to indicate that perhaps the Red Sox place a greater emphasis than most on the matchup when it comes to choosing their stolen-base attempts. This isn't something we can tell for sure; what we can tell for sure is whatever Boston's doing on the bases this year, it's working.