Masters Cup underway

The Tennis Masters Cup started today over in Shanghai. There are 8 players in the tournament, and they're split into two groups. The red group is comprised of Federer, Roddick, Murray, and Gilles Simon, who is a replacement for Nadal, who withdrew due to exhaustion. The gold group is comprised of Djokovic, Davydenko, Jo-Wilfried Tsonga, and Juan Martin del Potro. I believe they play a round-robin format, where each person plays everyone in his group, and then the two best records per group make up the semis. The gold group played today; Djokovic beat del Potro, and Davydenko won a close match against Tsonga. Tomorrow the red group plays; Federer will take on Simon, and Roddick will match up against Murray.