He was on the receiving end of a Shonie Carter spinning backfist.
I also think Serra will be in the finals but I'm not about to look it up and spoil it for myself. If GSP were to win the Welterweight title, I think Serra could very well win that. You do remember that GSP got caught with a Matt Hughes armbar. You have to wonder what Serra could do to GSP on the ground if Hughes could pull off a high-level jiu-jitsu counter like that.