One series that stands out on the schedule this week will be a short one, but also one of the more intriguing.The Mariners, winners of four straight, are playing the Astros in Houston tonight and Wednesday, and Seattle will begin the quick two-gamer in first place in the American League

One series that stands out on the schedule this week will be a short one, but also one of the more intriguing.

The Mariners, winners of four straight, are playing the Astros in Houston tonight and Wednesday, and Seattle will begin the quick two-gamer in first place in the American League West division. The Mariners are up a game up on the Astros, who, at the 61-game mark last year, were ahead by 13 games in a division race that never materialized to include any of the other four teams.

This year, Houston has its challengers, including Seattle, which has sole possession of first place in the AL West for the first time this late in a season since entering play on Aug. 25, 2003, when it had a one-game lead over the Athletics.

But it's notable that the Mariners are doing this while walking an offensive tightrope. Their plus-17 run differential ranks 14th in baseball, among 16 teams that have a positive ratio. The Astros, on the other hand, have a run differential that is more than 100 runs better -- their plus-122 ratio is tops in baseball.

How the teams have fared in close games is telling. Seattle has played 27 one-run games, posting an 18-9 mark, and haven't lost any of its six extra-inning contests. The Astros are 4-12 in 16 one-run games, and have lost four of five that have gone to extras.

Biggest jump: The Cubs jumped seven spots, from No. 11 to No. 4. The Cubs have won eight of their past 10 games, including a four-game sweep of the Mets in New York over the weekend. During this 10-game span, Cubs starters are second in the NL with a 2.78 ERA and have the fourth-lowest WHIP at 1.11. The Cubs 'pen has been good during this 10-game stretch, too, posting a 1.62 ERA, and offensively, hitters have posted a collective .842 OPS, second-highest in the NL, behind only the Rockies. Chicago has also pulled off some daring baserunning.

Biggest drop: The Phillies dropped six spots, from No. 8 to No. 14. The Phillies are in a bit of a tailspin, having lost seven of their past 10, including a weekend sweep by the Giants that featured exactly one Phillies run. In fact, entering their finale Sunday in San Francisco, the Phillies were slashing .205/.268/.339 over their prior 15 games, averaging 2.9 runs per contest.

Power Rankings Top 5:

1. Red Sox (1 last week)

At 41-19, the Red Sox are off to their best 60-game start since their 99-win season in 1978. They split a four-game series in Houston, concluding the series with a definitive 9-3 win over the defending World Series champs. Andrew Benintendi continues to pace the top of the order with scorching numbers -- in his past nine games, he's batting .417 (15-for-36) with nine extra-base hits and 11 RBIs.

2. Yankees (2)

After splitting a doubleheader with the Tigers on Monday, the Yankees have the second-best winning percentage in baseball at .679, just a tick behind the Red Sox (.683). Brett Gardner has been heating up of late, batting .377 (27-for-74) with 14 runs scored and 12 extra-base hits in his past 18 games.

3. Astros (3)

The Astros are in the middle of a challenging part of their schedule, having played four games in Cleveland (2-2 series split), three at Yankee Stadium (1-2) and four at home with the Red Sox (2-2). After the upcoming two games with the Mariners, the schedule eases up a bit. The bullpen has been an issue during this recent stretch -- over the past nine games, Houston relievers have allowed 18 earned runs over 30 1/3 innings for a 5.34 ERA.

4. Cubs (11)

May was a good month for the Cubs, who have jumped over a couple of teams in the tight NL Central to move within two games of the first-place Brewers. Cubs hitters hit a collective .273 in May, the second-best mark in the NL, behind the Giants (.281). Their .356 on-base percentage and .457 slugging percentage were tops in the NL.

5. Brewers (4)

The Brewers lost two of three to the White Sox over the weekend, but that's barely a blemish on what has been, so far, a fabulous season. The Brewers have the best record after 60 games in franchise history (37-23), breaking the mark of 35-25 held by the 2014 club. The key has been the bullpen, which has the third-lowest ERA in baseball at 2.68, behind the D-backs (2.48) and Cubs (2.59).

The rest of the Top 20:

6. Braves (5)

7. Mariners (6)

8. Nationals (7)

9. Cardinals (10)

10. Indians (12)

11. Angels (9)

12. D-backs (15)

13. Dodgers (14)

14. Phillies (8)

15. Rockies (13)

16. Athletics (17)

17. Pirates (16)

18. Twins (NR)

19. Giants (18)

20. Blue Jays (20)