This is what sucks about MLS. it;s hard to have meaningful competition for places because of the roster restrictions and cap limit. So if someone like Serioux is being a dick in practice, he's going to get picked anyway because there's no real alternative. And he also knows he's Canadian so it's harder for TFC to trade him away if the coach gets pissed off. So he can just mooch along, do the bare minimum in practice to get by and that's that.

I don't know if this scenario is true or not, it's just a hypothesis based on jloome's inside info, but you can see how it would fit together.