I saw the replay Sat night when Franck Songo'o of the Timbers tugged at the Chivas jersey's player. I believe Franck got a yellow card for it. Soon after that call Chivas scored. Seriously? This wasn't a bad tackle slide by Franck or something.
Tugging on an opponents jersey from behind in the attacking third is an automatic yellow card. Sometimes the refs chicken out and don't call it though.