This week's MLB Power Rankings show a slight shift in the middle of the pack, but little has changed at the top. The Cubs and Nationals, while not quite reaching in May the almost superhuman levels earned from their April performances, are still, by our calculations, the best of the best. Threats are coming, however -- keep an eye on the streaking Giants and two more early-season pleasant surprises -- the Chris Sale-led White Sox, and a Mariners team that is 21-9 in its last 30 games.
Biggest jump: Three teams jumped six spots: the Giants (10th to fourth), Indians (15th to ninth) and Rays (20th to 14th). In this space, let's focus on the Indians, whose 12-8 May has pushed them over .500 and to second place in the American League Central. They're in front of a whole mess of teams who were expected to be better than they're performing: the suddenly mediocre Royals, the flailing Tigers and the struggling Twins. A sweep of the Tigers earlier this month and a recent four-game sweep over the Reds gives the Tribe a good springboard, but they'll be tested soon enough, finishing off the month with three hot teams: the White Sox, Orioles and Rangers.

Biggest drop: The Blue Jays dropped a whopping eight spots, from 11th to 19th, although that might be a little harsh. Yes, the Blue Jays have dropped six of their last 10 and are struggling mightily offensively. But, these rankings are as much about where we envision teams being positioned at the end of the season as they are about what's happening in present times, and it may be somewhat short-sighted to write off Toronto merely as the 19th-best team in baseball. Stay tuned.

The Top 5
1. Cubs: The Cubs won their 29th game on May 20. A year ago, en route to a 97-win season, their 29th win arrived on June 6. The year before, on June 17. The year before that, June 18. You get the picture. The Cubs, despite coming down to earth a bit in the last couple of weeks by losing a double header at Wrigley Field to the Padres and dropping a recent series to the Brewers, are still without question the best team in baseball. They're going to have to pick up the pace a little if they're going to break the all-time record for single-season wins. But when a team is on pace for only 111 wins, it's apparent something special is cooking.

2. Nationals: Like the Cubs, the Nats showed they are actually human in the last couple of weeks, especially during a four-game sweep in Chicago early in May. But more recently, the Nats won a series over their most threatening division rivals, the Mets, wining the final two games by scores of 7-1 and 9-1. The offense, save for Daniel Murphy's whopping .387 average, has actually been underperforming by Nats standards, but that doesn't matter much when a team pitches better than almost anyone else. The Nats' 2.79 ERA is the second lowest in baseball and they are tops with 412 strikeouts.

3. Red Sox: The Sox earned top five status based on an offense that, at this pace, could be record-setting by season's end. They lead the Majors in hits, doubles, batting average, OPS and extra-base hits. They have homered at least once in 22 straight games. Jackie Bradley Jr. has a 27-game hitting streak. Heck, even the retiring David Ortiz can't be stopped, falling at triple short of the cycle on Sunday. Long-term, it'll be up to the pitching to keep Boston chugging toward the playoffs, but for now, the lineup has already provided a season's-worth of entertainment.

4. Giants: Including their 1-0 win over the Cubs on Sunday night, the Giants have reeled off 10 wins in 11 games, a stretch that included an eight-game winning streak. Through the streak, starters were 5-0 with a 1.34 ERA and the bullpen was 3-0 with a 2.93 ERA. Overall, the Giants have the sixth-lowest ERA in the National League at 3.83. Their team WHIP is 1.29. Their offense has still yet to click, but with the pitching they're produced, slow bats are hardly a concern. The first five weeks of the season left us wondering when and if any team would pull away in the NL West. The Giants, so far, appear to have given us the short-term answer.

5. Orioles: The knock on the Orioles as Spring Training came to a close was that they had a lineup full of mashers and a rotation void of aces. The only O's pitcher from 2015 who pitched to a sub-4.00 ERA was Wei-Yin Chen, and he's now a Marlin. Predictions largely rested on the Orioles scoring eight runs every night and allowing nine. Looks like the joke's on us. Yes, the O's are indeed mashing, but -- eureka! --- they're pitching, too. Through Sunday, they had the sixth-lowest ERA in the AL 3.80. And they're in first place in a surprisingly pedestrian AL East.

The rest
6. Mariners (7)
7. White Sox (3)
8. Mets (4)
9. Indians (15)
10. Rangers (8)
11. Pirates (9)
12. Phillies (16)
13. Cardinals (13)
14. Rays (20)
15. Royals (18)
16. Dodgers (12)
17. Marlins (14)
18. Yankees (NR)
19. Blue Jays (11)
20.Tigers (19)