Thomas McNamara, David Villa and Kwadwo Poku scored second-half goals and New York City FC beat D.C. United 3-1 on Thursday night in their inaugural matchup.
Lloyd Sam scored in the 90th minute and New York tied D.C. United 2-2 on Saturday night.
The 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.
The New York Red Bulls drew 1-1 in the away leg against DC United in the opening round of the MLS Playoffs.
The Red Bulls defeated the Union 3-0 on Saturday and have virtually wrapped up third place in the MLS East.
The New York Red Bulls have acquired defender Carey Talley from D.C. United for a conditional second-round 2011 draft pick.