If we've learned anything the first 4 1/2 months of the season, it's that the races that have yet to be decided are both plentiful and intriguing, and the final six weeks -- with an emphasis on the last two -- are setting up to be wildly entertaining.
The American League West and all three National League divisions are up for grabs, and the leads seemingly change hands daily. Even the Cubs, who, comparatively speaking, have a mildly stable 3 1/2-game lead, can't feel all that comfortable, given they can't seem to fully shake the second-place Brewers, while the Cardinals, as red-hot as any emerging team in the second half, may be the biggest division threat.
Meanwhile, who predicted the A's would be challenging the Astros in the AL West this late in the season? Not long ago, they were behind by double digits, but Oakland continues to be one of the best teams in the second half, posting a 19-8 mark since the All-Star break, making up a ton of ground on Houston, which is 11-14 over the same stretch.
Biggest jump: The Cardinals jumped six spots, from No. 14 to No. 8, which, not so coincidentally, dovetails with their emergence in both the division and Wild Card races. The Cards have won 10 or their past 12 games, outscoring opponents 73 to 31 during that stretch. Also, starting pitchers have posted a cumulative ERA just over 2.00 in those 12 games.
Biggest drop: The Dodgers dropped five spots, from No. 6 to No. 11. They won in landslide fashion on Sunday, beating the Mariners, 12-1. But lately, they've underperformed. The Dodgers have lost seven of their past 11 games dating back to Aug. 8, the day Kenley Jansen's final outing before being placed on the disabled list. Over the first 10 games without Jansen, the bullpen compiled a 5.52 ERA and blew leads or ties nine times.
Power Rankings Top 5
1. Red Sox (1 last week)
Even with their 2-0 loss to the Rays on Sunday, the Red Sox are 44-16 at Fenway Park this season, and have won 20 of their past 24 home games. The quiet day offensively resulted in the end of J.D. Martinez's home on-base streak, which peaked at 51 games Saturday. Overall, Boston has scored five or more runs a Major League-best 73 times, with a 63-10 record in those games. Outfielder Andrew Benintendi has 45 hits in his past 129 at-bats (.349), spanning 33 games.

2. Yankees (3)
Including their landslide win over the Blue Jays on Sunday, the Yankees are now 32 games over .500, their high-water mark of the season. J.A. Happ, acquired from the Blue Jays at the non-waiver Trade Deadline, has been fantastic as a Yankee -- he's 4-0 with a 2.23 ERA in four starts. He had a good day against his former team Sunday, allowing two runs over 5 1/3 innings with eight strikeouts.

3. Astros (2)
The Astros regained the lead in the AL West race on Sunday with a win over the A's, but Houston has lost seven of its past nine, scoring a total of 18 runs in those defeats. The Astros can take comfort, however, that the band is slowly getting back together. Carlos Correa has been off the DL for about a week, and George Springer rejoined the team when it started the current road trip last Friday. Jose Altuve has departed on a rehab assignment and is due back soon.

4. Indians (5)
The Indians have lost only one series since the All-Star break, and though they aren't fueled by the adrenaline rush of a division race -- they're the only team in the AL Central with a winning record -- they do have a reason to play with some sense of urgency as August turns into September. Cleveland has just three more losses than Houston, and with one of the easier remaining schedules in the Majors, there is a chance the Indians could end up with a better record than the AL West champion, which would enable them to host the AL Division Series. If the postseason began today, the Astros would host the Tribe.

5. Cubs (4)
Benjamin Zobrist is sizzling, posting the best average in the Majors since the All-Star break, but others -- namely, Javier Baez and Addison Russell -- have struggled of late. But the Cubs have made up for what's lacking offensively through their pitching, which entered Saturday's game having thrown 20 consecutive scoreless innings. They followed that by holding the Pirates to two runs over the final two games of the four-game series. The Cubs are going to be on a reprieve coming up -- starting Tuesday, they'll play nine games against sub .500 teams -- the Tigers, Reds and Mets.

The rest of the Top 20
6. A's (7 last week)
7. Braves (10)
8. Cardinals (14)
9. D-backs (9)
10. Phillies (8)
11. Dodgers (6)
12. Mariners (11)
13. Brewers (12)
14. Rockies (17)
15. Nationals (13)
16. Rays (15)
17. Pirates (16)
18. Giants (18)
19. Angels (19)
20. Jays (NR)