Jozy Altidore -- Chad Marshall -- MLS Cup 2016

Toronto FC and the Seattle Sounders may be considered favorites in their respective conference finals in the Audi 2017 MLS Cup Playoffs.

However, history suggests at least one of the last year's MLS Cup finalists won't return to the 2017 MLS Cup Final

At least one lower-seeded side has advanced from the Conference Championship in every edition of the Audi MLS Cup Playoffs since the round shifted to a two-leg, aggregate goals format for the 2012 season.

In 2012 and 2015, both lower seeds advanced to the final, meaning overall just three of 10 higher seeds have advanced since Conference Championships have been contested over two legs.

Overall, both higher seeds have advanced from their respective Conference Championship series just six times during 21 previous MLS seasons. And it hasn't happened since the Houston Dynamo and New England Revolution accomplished the feat in 2007.

What's it all mean? Well, in the context of the current format, the first leg is everything.

Higher seeds have earned a win or a draw in the first leg of the Conference Championships only twice, and they advanced both times. The only higher seed to overcome a first-leg defeat was Toronto FC last year in their memorable series with derby rivals Montreal Impact.

Perhaps past higher seeds have shown a bit of tactical naivety at the finals stage in the current format. Because their overall record, on the road in opening legs is 1W-8L-1D.

By contrast, lower seeds are 2W-5L-3D when they hit the road for the second legs with those leads, which suggests that by that point, playing for a tie on the road – or even a one-goal defeat – often works out  for them.