The Superstar Effect
scienceblogs.com
scienceblogs.com
...but of course it applies everywhere
In other words, if we see the opponent as within reach, or even just a little out of reach, we will struggle to get there. However, if we see the opponent as completely unreachable, it would be foolish to expend energy on an impossible task!
And as whatwhatwhat said, this effect applies EVERYWHERE. The psychological impact of 'first blood' in a fight, or shock-and-awe campaigns and other morale issues in armed forces also comes to mind.
I agree with the perceived skill though. During the Winter Olympics and curling, everyone thought they could do better. Probably not so much, but people feel that they can.