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, June 29.

Rankings from last week are in parenthesizes.

1. (1) Oakland Athletics – 4.26

The Athletics have won eight of their last 10 games, maintaining their dominance in the American League West.

2. (2) Los Angeles Dodgers – 4.10

Los Angeles trailed San Francisco by nearly 10 games at one point this month. They entered Monday's action tied atop the National League West.

3. (3) Washington Nationals – 3.82

The Nationals, who have a .689 OPS (22nd in baseball), will get Bryce Harper back this week.

4. (6) Milwaukee Brewers – 3.77

Jonathan Lucroy has keyed Milwaukee's offense with a .334/.403/.515 slash line and 3.7 oWAR.

5. (9) Detroit Tigers – 3.64

Miguel Cabrera suffered from a "down" month (.339/.460/.799 with three home runs and 15 RBIs) in June after posting an amazing .423/.704/1.126 line in May with eight HRs and 34 RBIs.

6. (8) Los Angeles Angels – 3.58

T7. (4) San Francisco Giants – 3.54

-- (10) Atlanta Braves – 3.54

9. (5) Toronto Blue Jays – 3.53

T10. (7) St. Louis Cardinals – 3.51

-- (11) Seattle Mariners – 3.51

T12. (T12) Pittsburgh Pirates – 3.39

-- (16) Cincinnati Reds – 3.39

14. (T12) Baltimore Orioles – 3.37

15. (15) Miami Marlins – 3.17

16. (18) Kansas City Royals – 3.16

17. (20) New York Mets – 3.14

18. (14) Boston Red Sox – 3.13

T19. (21) Cleveland Indians – 3.11

-- (22) Tampa Bay Rays – 3.11

21. (17) Chicago Cubs – 3.09

22. (19) Colorado Rockies – 3.02

23. (23) New York Yankees – 2.98

24. (24) Philadelphia Phillies – 2.88

25. (25) Chicago White Sox – 2.87

26. (26) Houston Astros – 2.85

27. (28) San Diego Padres – 2.71

28. (30) Arizona Diamondbacks – 2.62

29. (29) Texas Rangers – 2.54

30. (27) Minnesota Twins – 2.52

Follow @RealGMBaseball on Twitter and 'Like Us' on Facebook!