Some intriguing Major League Soccer storylines to watch this weekend:
The rivalry between Cascadia Cup foes Seattle Sounders and Portland Timbers is as passionate as any in MLS. But this edition, coming as it does with the season two-thirds complete, has more than just mere bragging rights at stake. There are significant Supporters' Shield and playoff implications, as well.
Seattle may have the highest points-per-game average in MLS, and with a game in hand on its Suppo...