How teams fare during the remaining 2 1/2 months of the regular season will determine who's playing baseball and who's playing board games at home come the middle of October.
Here's a look at nine key series in the second half of the season:
Phillies (48-38) at Marlins (46-44), July 16-19:
The race for the National League East title continues Thursday in Miami. The first-place Phillies lead the Marlins by four games heading into the four-game series. If Marlins shortstop Hanley Ramirez and Co. expect to leapfrog the Phillies sometime this summer, they are going to have to pick it up. Philadelphia leads the season series 4-2 and has outscored Florida 36-23. Jamie Moyer (8-6) takes the mound for the Phillies in the series opener against Florida's Chris Volstad (6-8).
Tigers (48-39) at White Sox (45-43), July 24-26:
This race for the AL Central title and possibly a Wild Card berth could come down to the wire but it all starts in July. The Tigers entered the All-Star break in first place, 3 1/2 games ahead of the White Sox and four games ahead of the Twins (45-44). The Tigers and White Sox split eight games during the first part of the season with the White Sox outscoring the Tigers, 37-33.
Red Sox (54-34) at Yankees (51-37), Aug. 6-9:
When these two teams square off against each other, it is always an event -- especially with the division on the line. The AL East-leading Red Sox have made quick work of the Yankees this year, winning all eight of their meetings in the first half of the season. The mighty Yankees offense has fizzed against the Red Sox so far this year, outscored 55-31. However, New York remains within striking distance, only three games out of first place. What has helped the Yankees this season is a stellar record (16-5) against the AL Central.
Dodgers (56-32) at Giants (49-39), Aug. 10-12:
The National League West-leading Dodgers have the best record in baseball and have succeeded despite playing without slugger Manny Ramirez for 50 games. How Ramirez responds after the layoff will have a big effect on the Dodgers' success in the coming summer months. With a staff that includes 2008 NL Cy Young Award winner Tim Lincecum and an improving Barry Zito, the Giants can flat out pitch. Need proof? Jonathan Sanchez threw a no-hitter July 10 in his first start after being demoted to the bullpen June 22. The Dodgers lead the season series against the Giants, 5-4.
Phillies (48-38) at Mets (42-45), Aug. 21-24:
Philadelphia led the season series 6-4 and outscored the Mets, 44-36, at the All-Star break and will be looking to build on its record in late August. The Phillies will be counting on their solid bullpen and more consistent performances from staff ace Cole Hamels down the stretch. However, a four-game series at home could be exactly what the Mets need heading into the final month of the season. A healthy Carlos Delgado and Carlos Beltran could make for an interesting series between rivals.
Red Sox (54-34) at Rays (48-41), Sept. 1-3:
Not that the Red Sox will need any extra motivation to start the final full month of the regular season, but it has to be hard to forget that the Rays ended Boston's playoff run in the American League Championship Series last season. Tampa's success carried over into the first part of the season. In the first 10 matchups between the two clubs, the Rays won six of them. During that stretch, the Rays outscored the Red Sox by a commanding margin, 64-41.
Cardinals (49-42) at Brewers (45-43), Sept. 7-9:
Propelled by first baseman Albert Pujols, the Cardinals led the Brewers by 2 1/2 games for the top spot in the competitive NL Central at the All-Star break. The Brewers won five out of the first nine games between the two teams despite being outscored, 31-27. The Brewers don't have CC Sabathia to lead the charge into the playoffs, but the club does have Prince Fielder, Ryan Braun and solid cast of young players.
Rangers (48-39) at Angels (49-37), Sept. 28-Oct.1:
The winner of the final series between the two teams currently on top in the American League West could be crowned the division champion. The Rangers held the top spot in the division for a 50-day stretch until the Angels overtook them in late June. The Rangers rallied in early July to regain first place but the Angels entered the All-Star break with a 1 1/2-game lead in the division. At the All-Star break, the Rangers had won seven of nine games between the two clubs.
Yankees (51-37) at Rays (48-41), Oct. 2-4:
In a series that could either determine the AL East champion and/or affect the AL Wild Card berth, these final four games matter. The clubs split the first four games against each other in 2009, but the Rays outscored the Yankees, 47-41. A strong finish in the regular season could propel the Rays into the playoffs and possibly back to the World Series.