They are No. 1 in their respective conferences and one of them could become the first MLS club to qualify for the 2013 MLS Cup Playoffs.

The New York Red Bulls (15-9-6, 51 pts.) and Seattle Sounders (15-8-5, 50 pts.) meet at CenturyLink Field on Sunday night (9 pm ET, ESPN) in one of the biggest matches of Week 31. And the team that emerges victorious will not only take a big step toward the Supporters' Shield, but they could also clinch a postseason berth.

The problem for the Sounders is that they would not be able to celebrate making the playoffs until much later on Sunday night since their berth hinges on the result between Chivas USA and the San Jose Earthquakes (11 pm ET on MLS LIVE).

Here are the scenarios as outlined by the MLS league office, in which a tie could also be enough to clinch a playoff spot for RBNY with the right combination of results:

NEW YORK RED BULLS can clinch berth to MLS Cup Playoffs by beating Seattle AND:

Philadelphia Union tie or lose vs. Sporting KC (Friday, 8 pm ET on NBCSN) OR Chicago Fire tie or lose vs. Montreal Impact (Saturday, 8:30 pm ET on MLS LIVE)

NEW YORK RED BULLS can clinch berth to MLS Cup Playoffs by tying Seattle AND:

Philadelphia Union lose vs. Sporting KC (Friday, 8 pm ET on NBCSN) OR Chicago Fire lose vs. Montreal Impact (Saturday, 8:30 pm ET on MLS LIVE)

SEATTLE SOUNDERS can clinch berth to MLS Cup Playoffs by beating Red Bulls AND:

FC Dallas lose vs. Columbus Crew (Sunday, 8:30 pm ET on MLS LIVE) AND San Jose Earthquakes lose vs. Chivas USA (Sunday, 11 pm ET on UniMas)