The Opsera is a statistic RealGM Executive Editor Chris Reina created in order to objectively rank teams by how well they hit (OPS) and pitch (ERA). 

In order to determine the Opsera rating for each, we take their OPS, multiply that number by 10 to move the decimal point over one place to the right and then subtract their ERA from that number.  

All statistics are through Sunday, May 18.

Rankings from last week are in parenthesizes.

1. (2) Oakland Athletics – 4.73

The Athletics have a +95 run differential, forty runs greater than the next-highest mark (Detroit).

2. (3) Detroit Tigers – 4.44

Detroit, who just swept the Red Sox in Boston, have baseball's best road record (14-4).

3. (1) Colorado Rockies – 4.31

At Coors Field, the Rockies have a .981 OPS and average 7.33 runs per game.

4. (5) San Francisco Giants – 3.95

Michael Morse continues to be a difference-maker for the Giants. He's hitting .277/.329/.534 with 10 home runs and 28 RBIs in 45 games. His $6 million salary is looking like a bargain.

5. (4) Atlanta Braves – 3.79

Concerns over all the injuries to Atlanta's staff are long gone. They have the lowest ERA (2.82) in the Major Leagues.

6. (9) Washington Nationals – 3.76

Washington jumped three spots in our rankings after winning four of six last week. 

T7. (6) Los Angeles Dodgers – 3.74

Even after a long home run on Sunday, Adrian Gonzalez is hitting just .212/.316/.318 in the month of May.

-- (10) Miami Marlins – 3.74

The Marlins are surviving without Jose Fernandez so far because Tom Koehler (2.25 ERA), Nathan Eovaldi (3.62 ERA, 50 Ks) and Henderson Alvarez (3.62 ERA) have all pitched very well.

T9. (T7) Milwaukee Brewers – 3.73

Milwaukee has cooled down, but they still have a nice cushion in the National League Central.

-- (T7) Los Angeles Angels – 3.73

Albert Pujols already has 12 home runs, second in the AL. He had 17 homers all of last season.

11. (11) St. Louis Cardinals – 3.44

12. (14) New York Yankees – 3.35

13. (13) Boston Red Sox – 3.25

14. (15) San Diego Padres – 3.24

15. (17) Kansas City Royals – 3.23

16. (19) Toronto Blue Jays – 3.20

17. (12) Cincinnati Reds – 3.17

18. (21) Seattle Mariners – 3.10

T19. (16) Pittsburgh Pirates – 3.08

-- (24) Chicago Cubs – 3.08

21. (25) Philadelphia Phillies – 2.95

22. (20) Baltimore Orioles – 2.94

23. (18) Cleveland Indians – 2.85

24. (22) Tampa Bay Rays – 2.76

25. (27) New York Mets – 2.63

26. (26) Texas Rangers – 2.61

27. (23) Chicago White Sox – 2.60

28. (28) Minnesota Twins – 2.46 

29. (29) Arizona Diamondbacks – 2.40

30. (30) Houston Astros – 2.31

 

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