When the Pirates and Nationals began their three-game series in Washington on Monday, one of them was in a fight for first place. The other had just a few wins more than the last-place team in their division.
It's unlikely many could have predicted it would be the Bucs with the winning record. They're within striking distance of the first-place Cubs, while the Nats are three games under .500, with only two fewer losses than the rebuilding Marlins.
It's been that kind of start to the season. Several projected contenders -- the Nationals, Dodgers and Twins, for example -- are all at least three games under .500, while team like the Braves, Phillies and Pirates are a collective 14 games over .500.
This week's Power Rankings reflect this. Dramatic shifts have changed the look of the top 10, while several high-ranking mainstays find themselves creeping closer to the bottom.
Biggest jump: To the best of our recollection, no team has ever jumped 10 spots in one week. This week, we have two. The Bucs leaped from No. 17 to No. 7, and the Braves went from No. 18 to No. 8.
During a five-game winning streak that ended Monday, the Pirates outscored opponents, 26-10. Their bullpen threw 15 1/3 scoreless innings and added two more in their 3-2 loss to the Nats on Monday. Catcher Francisco Cervelli is batting .385 (10-for-26) with eight RBIs over his last eight games.
The Braves, who were off Monday, have won four of their past five games, dating back to last Wednesday -- the day they called up top prospect Ronald Acuna Jr. The outfielder is 8-for-19 (.421) with five extra-base hits, three runs and four RBIs in his first five games.
Biggest drop: The Nationals, as one of the above-mentioned contenders struggling in the early going, dropped nine spots (from No. 8 to No. 17). But the Angels also had a big fall of seven spots, going from No. 6 to No. 13. They looked like they might have worked out of their troubles when they followed a streak of five losses in six games with a series win in Houston, but the good times ended there. They were swept at home over the weekend by the Yankees, including an 11-1 loss on Saturday. And no bullpen in the Majors has thrown more innings this season than the Angels, whose relievers have tallied 124 innings.
(Also notable: The Dodgers, who lost shortstop Corey Seager for the season to Tommy John surgery, fell five spots, from No. 10 to No. 15.)
Power Rankings Top 5
1. Astros (2 last week)
After one week in the second slot, the Astros are back to being the top team in baseball, though Houston and Boston are pretty much interchangeable. The Astros recovered from a series loss to the Angels to take two of three from the surging A's. They lead baseball in ERA (2.54), strikeouts (316) and opponents OPS (.598) and received a sterling start on Monday from Charlie Morton, who allowed one run on two hits with 10 strikeouts over 7 2/3 innings.

2. Red Sox (1)
The Red Sox won 19 of their first 25 April games. It's the first time they've ever won as many as 19 games in the first full month of the season. And how good has J.D. Martinez been? He was 4-for-4 on Sunday and 2-for-4 on Monday and is now 11-for-22 with a homer and seven RBIs in his past seven games. Martinez has been especially terrific at Fenway -- 19-for-52 with eight extra-base hits and 15 RBIs, including Monday night, in 13 games in Boston.

3. D-backs (3)
Arizona has won each of its first nine series to begin the season. There has only been one other National League team to do that -- the 1907 Cubs, who won their first 11 series. The D-backs will be tested coming up, though. Their next four series are with the Dodgers (twice), Astros and Nationals.
With his impressive 10-strikeout performance in a win over the Dodgers on Monday night, Zack Greinke is 15-1 in 21 starts at Chase Field dating back to the start of 2017. Greinke has baseball's highest home winning percentage (.938) in that span.
4. Yankees (9)
The Yankees jumped five spots, thanks to a nine-game winning streak that began with two wins against the Blue Jays, continued with sweeps of the Twins and the Angels and ended with Monday's 2-1 loss in Houston. Shortstop Didi Gregorius leads baseball in RBIs (30) and wRC+ (207), is tied for first with 10 home runs and is second in OPS (1.156).

5. Cubs (11)
Welcome back to the Top 5, Cubs. A two-game split with Cleveland and a four-game sweep at home over Milwaukee rightfully pushed them higher in the rankings, especially considering the scores of the wins against the Brewers: 1-0, 3-2, 3-0, 2-0. The Cubs have played the Brewers eight times this year and have allowed nine runs. Total.
The Cubs also strung together 24 scoreless innings before yielding two to the Rockies in the fifth inning Monday.

The rest of the Top 20
6. Mets (4 last week)
7. Pirates (17)
8. Braves (18)
9. Indians (5)
10. Phillies (14)
11. Cardinals (7)
12. Blue Jays (12)
13. Angels (6)
14. Mariners (19)
15. Dodgers (10)
16. Brewers (13)
17. Nationals (8)
18. Rockies (15)
19. Athletics (NR)
20. Giants (20)