Last week, The Motley Fool introduced its Baseball Efficiency Standings. The ranking system, also known as "B.E.S.T.," is designed to determine the sport's best teams according to financial efficiency. By comparing on-field performance with payroll, it's possible to see who's getting the most -- and the least -- bang for their buck. Now, it's time for an update.

Through the first 10 days of May, many of MLB's most efficient teams are also playing the best ball.

Baseball Efficiency Standings | Create Infographics

Four of the MLB's five most efficient teams -- the Miami Marlins, Oakland Athletics, Colorado Rockies, and Milwaukee Brewers -- would make the playoffs if the season ended today. The Marlins, in particular, are on pace for an 88-win season with a payroll of just $47.5 million, second lowest in baseball.

Who's the most improved team?
That honor -- at least in terms of payroll efficiency -- goes to the Chicago White Sox. As the standings illustrate, the South Siders are paying $1.1 million per win in 2014, significantly less than the $1.9 million each win cost last year. That's a difference of over 40% -- by far the biggest improvement in baseball. In 2013, the White Sox finished 27th out of 30 in payroll efficiency. This year, they're 10th. So why the success?

It starts with Jose Abreu.

Image via Robert Rescot, Flickr.

A rookie at the age of 27, there's little about the Cuban first baseman that's ordinary. Abreu defected to the U.S. last fall, and soon after signed with the White Sox for six years and $68 million. Many pundits questioned the move's risk, and rightly so. But in hindsight, it appears Chicago's front office was simply banking that Abreu's bat would adjust to Major League pitching.

While playing most of his pre-MLB career in the Cuban National Series, he won an MVP and set his league's single-season home run record. In 2011, his best year, Abreu hit .453 with 33 homers and 93 RBI in just 66 games. Although fellow defectors Yasiel Puig and Yoenis Céspedes might've gotten more hype, Abreu arguably entered the MLB with more upside.

And in 2014 thus far, the White Sox's gamble has paid off. Abreu slugged .613 with 10 home runs and 31 RBI in April, en route to the AL's player of the month and rookie of the month awards. Along with Puig, the two are the only rookies to accomplish the feat in their first month, according to ESPN.

Abreu's impact has been enormous
With a 162-game pace of 55 homers and 158 RBI, it's hard to ignore the impact he's had on his team's offense. The difference is night and day when compared to 2013.

 White Sox Offense, MLB Ranks
  2013 2014
Runs 29th 2nd
Hits 16th 2nd
Home runs 19th 5th
RBI 28th 2nd
Average 19th 3rd
Slugging 25th 5th


Above-average production from the likes of Alexei Ramirez, Dayan Viciedo, and Adam Eaton has also helped. But consider this: If Abreu's numbers were replaced by what Paul Konerko -- the team's previous first baseman -- put up last April, each of those offensive ranks would drop by about four spots. The White Sox are seeing the ball better this year, but it's Abreu who's made them elite.

Perhaps most interestingly, though, the team's pitching has gotten worse. Its aggregate ERA, including all starters and relievers, is over 4.50 this season. That's fourth worst in baseball, and about a half-run higher than 2013.

Taking a look at the bigger picture
With all else constant, it's clear why the White Sox are on pace to finish the season at 81-81, nearly 20 wins better than last year: Their Jose Abreu-led offense. And while this alone is cause for celebration, it's not the entire picture.

The White Sox have improved while lowering their payroll by more than 25%. In 2013, the team doled out $124 million to its players, according to Deadspin. This year, total payroll is just over $91 million.

Rick Hahn, the White Sox's GM, shared his thoughts with ESPN during the offseason:

Given where we're at right now, given that we're trying to get younger and with that comes a little bit more affordability, we don't think that even a modest decrease in the total expenditures on the baseball side is necessarily going to hurt our competitiveness…. In terms of the money there is more than enough to win.

This strategy has worked well. By letting go of Gavin Floyd and trading Jake Peavy last year, the team shed two of its highest priced pitchers -- they made a combined $13.5 million in 2013. Brett Myers' bloated contract is finally off the books as well. Now, three of the Sox's five starting pitchers -- Jose Quintana, Andre Rienzo, and Scott Carroll -- are making under seven figures this season.

On the offensive side, Abreu's arrival is important for another reason: It marks the end of the Paul Konerko era. After making over $13 million in 2013, the White Sox resigned their 38-year old captain to a final one-year, $2.5-million deal before he officially retires. Abreu is nearly $5 million cheaper this season than Konerko was last year.

The bottom line
At the end of the day, the Chicago White Sox have improved in the efficiency department for several reasons. Konerko's pay cut and a focus on cheaper, younger pitching have kept costs down. And Jose Abreu's otherworldly power has helped awaken the team's bats. There's still a lot of the 2014 season left, but as long as the Sox can remain near .500, they should finish the year as one of the "B.E.S.T." teams in baseball.