WASHINGTON -- The Nationals beat the Phillies on Tuesday night but didn't get any help from the Cardinals, leaving the No. 1 seed to be decided on the final day of the season.
Washington and Cincinnati remain tied for the best record in the National League -- and in baseball -- and a Nats win or a Reds loss on Wednesday will lock up the top spot for Washington. The No. 1 seed opens the Division Series on Sunday against the winner of the one-game Wild Card showdown; the No. 2 seed would open on Saturday in San Francisco .
If both teams win or both teams lose, the Nationals own the season tiebreaker and would earn the top seed.
Manager Davey Johnson rested most of his starters on Tuesday but expects to throw out his top group on Wednesday behind Edwin Jackson.
"I prefer not to fly out to San Fran just for two days, for just the travel purposes," said infielder Mark DeRosa. "But in 2010, that was exactly what [the Giants] did, and it was fine. It really doesn't matter once those games start. It's about who's going to execute and who's going to enjoy the moment instead of letting it get a little too big for them."
Wednesday's key game to watch
Reds (Bailey, 13-10) at Cardinals (TBD), 8:15 p.m. ET Preview >
If the postseason started today ...
This is how the teams would match up: Postseason Bracket »
To calculate a team's magic number, take the number of games it has remaining and add one. Then subtract the difference in the number of losses between that team and its closest pursuer.
A tiebreaker game will be played to determine a division winner, even if the tied clubs are assured of participating in the postseason. If a division championship tiebreaker is necessary, the head-to-head record between the clubs will determine home-field advantage. If the head-to-head record is tied, then the division record will be the next tiebreaker.
If two clubs are tied for the two Wild Card berths, home-field advantage will be determined by the head-to-head record between the clubs. If the head-to-head record is tied, then the division record will be the next tiebreaker.
Tiebreaker rules »
Complete schedule »
Joey Nowak is a reporter for MLB.com. Follow him on Twitter at @joeynowak. This story was not subject to the approval of Major League Baseball or its clubs.