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09/20/10 10:00 AM ET

Postseason Picture: Sept. 20

Nobody likes Mondays, but there's no reason not to like this one, with a key series in each league opening in New York and Philadelphia.

In both cases, the league's top club meets a divisional opponent with the second-best record. The Yankees have the best record in baseball, but they'll face a stern test from the Rays, who are a half-game behind them in the American League East. The Phillies are likewise the top club in the National League, and they host the Braves.

New York will send 23-year-old Ivan Nova to the hill to face Tampa Bay for the second time in a week. Nova pitched four strong innings but was knocked around badly in the fifth on Sept. 14, eventually yielding six runs on six hits in 4 2/3 innings. The Rays will counter with Matt Garza. This is the first installment of a series that could decide home-field advantage for the first two postseason rounds in the AL.

The Phillies have their rotation lined up ideally for their series against the Braves. Cole Hamels gets the call for Philadelphia in the opener, opposed by Jair Jurrjens. The Phils will follow with Roy Halladay and Roy Oswalt in the series' successive games. Hamels has fairly pedestrian numbers in his career against Atlanta (8-5, 4.25 ERA), while Jurrjens has a limited history of success against the Phils (3-3, 2.56 ERA). Keep this in mind: Bobby Cox's next win will be No. 2,500 in his career; he's fourth on the all-time list.

So there's still plenty of business that needs attending to on Monday. There's plenty of time for things to change in the two weeks before the regular season ends on Oct. 3. Three of the four Division Series are scheduled to begin on Oct. 6.

American League
All four likely postseason contenders from the AL will be in action, including the Yanks' meeting with the Rays. Minnesota can chop another game off its magic number of four when it sends lefty Brian Duensing to the hill against the Indians. Texas, which has a magic number of six to clinch the AL West, can do the same with Derek Holland on the hill against Jered Weaver and the Angels.

Duensing has been on quite a roll since he was elevated to the starting rotation. He's allowed three earned runs or fewer in nine of them, including a win over the Indians on Aug. 8. Minnesota is one game off the pace for the best record in the Majors, though it appears locked into a matchup with the Wild Card winner because of the rule that prevents intra-division play in Division Series.

National League
The showdown between the Phillies and Braves gets top billing on a day when the three NL West contenders take a breather. There are other intriguing matchups, however, with the Reds opening a three-game series against the Brewers and the Cardinals visiting Florida.

Given its six-game lead in the NL Central, Cincinnati has the luxury of thinking about things like postseason rotations. Right-hander Homer Bailey has the stuff to be an important piece for the Reds, but he's yet to translate that into consistency. Bailey will get a chance to state his case to make postseason starts when he faces the Brewers, who have given him fits in the past. Bailey has made five career starts against Milwaukee and has an 0-2 record and 6.44 ERA.

The Cardinals, meanwhile, need help to overcome their deficit to the Reds. St. Louis heads out on its final road trip of the season in Florida, where they'll make up a game that was postponed on Aug. 8. The Cards will need to buck a trend of struggling on the road this season if they want to make a run -- St. Louis is 31-43 away from Busch Stadium and 9-13 since Aug. 1. Chris Carpenter will make the start for the Cardinals against the Marlins' Chris Volstad.

Magic numbers
To calculate a team's magic number, take the number of games it has remaining on the schedule and add one. Then subtract the difference in the loss column between the team and its closest pursuer.

The Reds are the closest club in the NL to clinching a postseason berth. Cincinnati has 12 games remaining; adding one yields 13. The Reds have 66 losses to the Cardinals' 71, a difference of five. Subtract that from 13 to get the Reds' magic number: eight.

Tiebreaker scenarios
Additional games will be required in the event of ties atop the standings in any of the divisions or in the Wild Cards. Games would be played between the close of the regular season and the opening of the postseason.

If two teams are tied atop the division and both are assured of making the postseason, season-series record would be used to determine which team is the division champion and which falls to the Wild Card.

If two teams are tied atop the division and share the Wild Card lead with another club, the ties will be broken in the following fashion:

• The teams tied atop the division will play, with the winner taking the division.
• The losing team will then play the remaining Wild Card contender, with the winner making the playoffs in that spot.

If three clubs tie atop a division or Wild Card standings, each club would be designated in one of three slots, "A," "B," or "C," based on head-to-head record. Tiebreaking games would proceed like this:

• Club A hosts Club B on Monday, Oct. 4
• The team that emerges from the first game hosts Club C on Oct. 5, with the winner declared champion.

Key games to watch (all times ET)

Cardinals (Carpenter, 15-7) at Marlins (Volstad, 9-9), 3:10 p.m. Preview >
Braves (Jurrjens, 7-6) at Phillies (Hamels, 11-10), 7:05 p.m. Preview >
Rays (Garza, 14-8) at Yankees (Nova, 1-0), 7:05 p.m. Preview >
Orioles (Matusz, 8-12) at Red Sox (Matsuzaka, 9-5), 7:10 p.m. Preview >
Reds (Bailey, 3-3) at Brewers (Capuano, 3-4), 8:10 p.m. Preview >
Twins (Duensing, 9-2) at Indians (Gomez, 3-4), 8:10 p.m. Preview >
Rangers (Holland, 3-3) at Angels (Weaver, 12-11), 10:05 p.m. Preview >

If the postseason started today ...

Rangers (3) at Yankees (1)
Rays (Wild Card) at Twins (2)

Reds (3) at Phillies (1)
Braves (Wild Card) at Giants (2)
(The Giants and Reds have identical records of 84-66. The Giants would win the tiebreaker on the merit of their 4-3 season-series edge over Cincinnati and thus would receive the higher seed and face the Wild Card winner.)

Leaders and contenders


AL East
Yankees: L, 4-3 @ BAL
Lead: Half-game over TB | Next: vs. TB

AL Central
Twins: L, 6-2 vs. OAK
Lead: 10 over CWS | Next: vs. CLE

AL West
Rangers: L, 2-1 @ SEA
Lead: 9 over OAK | Next: @ LAA

AL Wild Card
Rays: L, 6-3 vs. LAA
Lead: 6 1/2 over BOS | Next: @ NYY

Top AL contenders
Red Sox: W, 6-0 vs. TOR
Deficit: 7 in AL East, 6 1/2 in Wild Card | Next: vs. BAL


NL East
Phillies: W, 7-6 vs. WAS
Lead: 3 over ATL | Next: vs. ATL

NL Central
Reds: L, 4-3 @ HOU
Lead: 6 over STL | Next: @ MIL

NL West
Giants: W, 9-2 vs. MIL
Lead: Half-game over SD | Next: @ CHI on Tuesday

NL Wild Card
Braves: W, 6-3 @ NYM
Lead: 2 1/2 over SD, 3 1/2 over COL, 8 over STL | Next: @ PHI

Top NL contenders
Padres: L, 4-1 vs. STL
Lead: Half-game behind SF in West, 2 1/2 behind ATL in Wild Card | Next @ LAD on Tuesday

Rockies: L, 7-6 @ LAD
Deficit: 1 1/2 behind SF in West, 3 1/2 behind ATL in Wild Card | Next: @ ARI on Tuesday

Cardinals: W, 4-1 vs. SD
Deficit: 6 behind CIN in Central, 8 behind ATL in Wild Card | Next: @ FLA

Sunil Joshi is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.