MLB Power Rankings: Bumgarner helps slug Giants to No. 3

Major League Baseball's first week of the season is in the books, and there's already some significant change at the top of our rankings. San Francisco was the big riser, jumping four spots, Baltimore moved up three ranks with its undefeated week, and St. Louis stumbled out of the gate and out of the top 10.

The composite rankings were compiled by theScore MLB editors Jonah Birenbaum, Bryan Mcwilliam, Simon Sharkey-Gotlieb, Dan Toman, and Greg Warren.

1. Chicago Cubs

The Cubs' impressive depth will be put to the test after Kyle Schwarber's injury, but they outscored the opposition by 27 runs on the road this week, so we're willing to bet they'll be OK.

2. Washington Nationals

Four games into the season and Bryce Harper is already having a Bryce Harper season. Baseball is fun again in D.C.

3. San Francisco Giants

From Trevor Brown's dramatic debut home run to Madison Bumgarner going deep off Clayton Kershaw, it felt like a World Series week for the even-year champs.

4. Toronto Blue Jays

The Blue Jays showed off their good side and bad side this week, and boy is that good side powerful.

5. New York Mets

The Mets are pitching like we thought they would (majors' second-best ERA), but unfortunately they're hitting like it, too (fewest runs scored in the NL).

6. Los Angeles Dodgers

A third of the Dodgers' lineup is on the DL, but at least Yasiel Puig is back to being awesome again.

7. Houston Astros

Tyler White's slugging percentage is higher than Josh Donaldson's OPS. Just to put the rookie's start in perspective.

8. Pittsburgh Pirates

The importance of Polanco's team-leading .538 OBP is only outdone by his new five-year deal. Good week for the Steel City.

9. Boston Red Sox

Red Sox starters not named David Price have allowed 18 runs in 19 2/3 innings this season.

10. Kansas City Royals

The under-appreciated Royals climbed into the top 10 by sweeping the Twins, and the defending champs could make a lot more noise this week with a four-game showdown looming in Houston.

11. Detroit Tigers

Even with Justin Upton scuffling at the plate, the Tigers still hit .300/.346/.467 through their first four games. In other words, they're going to score a LOT of runs this year.

12 Texas Rangers

Top prospect Nomar Mazara joins a battered outfield that's homerless with three extra-base hits in 82 plate appearances.

13. St. Louis Cardinals

It'd be much easier to slough off poor first weeks from Yadier Molina and Matt Holliday if they didn't have a combined age of 69.

14. New York Yankees

Castro is off to a torrid start in the Bronx, and the bullpen is already rolling, but it's a bit concerning the only starter to make it through six innings so far is CC Sabathia.

15. Cleveland Indians

Blame it on the rain? Cleveland's vaunted rotation has allowed six homers in 21 2/3 innings so far (2.49 per nine).

16. Seattle Mariners

Robinson Cano looks like Robinson Cano again, and it seems to be rubbing off on his teammates: The Mariners lead the AL with 11 homers thus far.

17. Baltimore Orioles

Adam Jones hasn't been in the lineup for more than half of Baltimore's undefeated schedule, but perhaps more surprising is that Tillman, Jimenez, and Gallardo each boast an ERA of 1.80 or better.

18. Chicago White Sox

Though neither Todd Frazier nor Brett Lawrie have done much yet, the first trip through the rotation (aside from John Danks) was plenty encouraging.

19. Arizona Diamondbacks

Greinke said he's "got to start pitching better" following a terrible first week in the desert, but he ain't the only one. Shelby Miller and Patrick Corbin had awful first starts, too.

20. Los Angeles Angels

Mike Trout has only four hits, and when he struggles, so do the Angels. After starting 2-4 at home, LA now hits the road for 10 games.

21. Tampa Bay Rays

Tampa's pitching staff may be the best in the AL East, but nobody is hitting besides Steven Souza and new cleanup man Corey Dickerson.

22. Colorado Rockies

Rookie Trevor Story's historic homer barrage is enough to push the Rockies up in the rankings, but this team still allowed a dreadful 8.5 runs per game during the opening week.

23. Miami Marlins

Miami is 1-3 through four games, but Fernandez and Stanton appear poised for healthy and productive seasons.

24. Minnesota Twins

Serious growing pains in Minnesota: The Twins scored nine runs last week, with Sano and Buxton combining for a .133 average and 54.5 percent strikeout rate.

25. Oakland Athletics

A very respectable start, and Oakland's makeshift rotation behind Sonny Gray is holding early. The Angels and Royals will visit the Bay Area this week.

26. Milwaukee Brewers

Closer Jeremy Jeffress is tied for the league lead in saves with three. Perhaps more surprising is the fact that Scooter Gennett is suddenly a power threat.

27. Cincinnati Reds

Nobody expected the Reds to jump out to a 5-1 start, or Eugenio Suarez to belt four homers and collect nine RBIs out of the gate.

28. San Diego Padres

Who are the Padres? Are they the team that got outscored 25-0 in its opening series with the Dodgers? Or, the squad that clubbed 29 runs in two games in Colorado?

29. Atlanta Braves

Watching Dan Winkler's elbow break on Sunday capped a wretched first week for the Braves, who are 0-5 for the first time since 1988.

30. Philadelphia Phillies

Jeremy Hellickson and Vincent Velasquez looked sharp in their debuts, and Ryan Howard is hitting home runs again, but it's still going to be a long season in Philly.

*Pythag record is a formula invented by Bill James in an attempt to determine how many games a team should have won based on runs scored and allowed.