Watching Federer battle Del Potro is like watching Tendulkar and Dhoni on two ends of the pitch. While Potro can get the ball across the net effectively it's clumsy to watch, especially when you have Federer on the other side performing a ballet.

Update: I spoke too soon - Federer's unforced errors in the fifth set exceeded what he's committed in this whole tournament. Kudos to Del Potro.

Truly a useless observation but I have to point it out: After Federer won his first set and was walking to his chair, he took the optimum route so that the towel boy from the court corner didn't have to cover a few extra steps, which also means that Federer didn't have to wait a few extra seconds to grab his towel. Interestingly, he won the set without breaking a sweat.

After beating Robin Soderling 6-0,6-3,6-7,7-6 to reach the semifinals of the US Open, Federer said "It was cold in the beginning and I felt at home. After a couple of sets it was even cooler and he must have felt at home."

For those scratching heads - Federer's from Switzerland and Soderling's from Sweden.