Player rating is a subjective activity. Players in different leagues will be judged differently for similar performances. A player outperforming his perception may score an eight where a known commodity might see a six. When a team like the Seattle Sounders turns off the engines and goes into a nosedive, simply pulling out of the drop is worth an extra point or two on the scale. To follow that same line of thinking, pulling up only to clip a wing on a jagged rock can, for a moment, seem worse than the near-fatal crash itself.
That metaphor had a few more layovers than necessary, but the point is that player ratings are massively results-based. Does anyone doubt that the last final minutes of the Olimpia match earned the entire roster higher scores? If two fluky Real Salt Lake goals don't find their way past Stefan Frei, what sort of overall grade are we looking at? Even pretty decent games from guys like Frei and Nelson Valdez will take a hit from what was ultimately a 2-0 scoreline.
This probably doesn't seem like some sort of revelation, and that's because it isn't. But you won't get me to talk about the actual game for two paragraphs, so... *exit stage left.*
Blank - player did not play enough to judge
1 - not a pro (USL/NASL/MLS) quality performance
4 - average USL starter
6 - average MLS starter
9 - MLS All Star
10 - MLS MVP-quality performance