How you can make a call out of that I never know.

You could argue:

a: It was a penalty (essein clearly contacted giggs)
b: Giggs fould cech
c: The ball went over the line so goal

There was no way a ref could have made a call, and whether giggs fouled cech is again very debatable as it was through being tripped that he fell into Cech, but he also one the ball then careered into cech. Had cech been an outifeld player I think it wouldn't be a foul, but as it was a keeper I think most refs would give a foul.

Anyway all academic. Poor game, nothing between the 2 teams, as the premier league showed. As ever when the 2 big teams meet the occassion/tactics just get the better of the game and a poor game results.