The New York Red Bulls have a chance to secure a spot in the Eastern Conference finals when they return home to their recovering region, but they may not have a key player available for that attempt.
D.C. United, meanwhile, are guaranteed to be short-handed for Wednesday night's second leg.
Because of power outages and flooding caused by Hurricane Sandy, Saturday's opener was shifted to the nation's capital, where the teams finished with a wild 1-all draw after own goals from both clubs.
Red Bulls goalkeeper Luis Robles came up big when he stopped Chris Pontius' penalty kick in the first half, then United salvaged the tie despite playing down a man for the final 19 minutes after Andy Najar was given a red card for throwing the ball at the referee.
"I liked the way we approached the game. I like the way we executed. We have to keep our heads up," Pontius said.
Najar, the 2010 MLS rookie of the year, is suspended for Wednesday's game while the status of New York's Rafa Marquez is unknown because of a calf injury suffered Saturday. The Red Bulls are expected to make a decision on their designated player following an MRI this week.
"It probably has to be a late decision," coach Hans Backe told the league's official website Monday. "I don't think it's a big one but we have to wait until (Tuesday) afternoon (or) evening until we know."
Marquez's potential absence could hurt New York's chances of eliminating D.C. for the first time in four all-time playoff matchups. United advanced from series in 1996, 2004 and 2006.
The Red Bulls prevailed 3-2 in their lone home game against United this season June 24 as former D.C. player Brandon Barklage scored a pair of first-half goals and Jan Gunnar Solli broke through in the 55th minute. Barklage is now out with a plantar fascia injury.
Pontius scored both of his team's goals in that game and recorded a hat trick against New York in a 4-1 home victory April 22. He finished with a team-leading and career-high 12 goals this season.
It's unclear if the Red Bulls' leading goal scorer, Kenny Cooper, will start in this game. Backe decided to go with Sebastien Le Toux at forward alongside Thierry Henry for Saturday's game to try to stretch D.C.'s defense, but Le Toux recorded only one shot and Cooper replaced him in the 80th minute.
"I'm definitely itching to get out there and hungry to play," said Cooper, who matched a career high with 18 goals this season. "Whether I play a minute or 90, I'll look to give my best for the team."
New York hasn't reached the conference finals since its run to the MLS Cup final in 2008. D.C., which snapped a four-year playoff drought this season, last made it that far in 2006.