Once upon a time, Bill Simmons came up with the idea of ranking all the players in the NBA by their trade value. Jonah Keri and Dave Cameron extended that idea to MLB. As far as I know, no one has attempted this for MLS. However, if they did, you might be surprised who ended up on top.
Cristian Roldan is not the best player in MLS. Cristian Roldan is not even the best player on the Sounders. Cristian Roldan might very well be the most valuable Sounder. Cristian Roldan might be the most valuable player in the entire league.