Anna Chakvetadze, who played a grueling, almost 3-hour match last night and had to have been both mentally and physically exhausted (she had an obvious leg cramp) was made to play in the early semifinal match today. An argument could be made that fitness is part of the game, but there aren't many players--if any--who could make that type of quick recovery from that type of match. The mental fatigue is probably as great as the physical.
A better argument is that Chakvetadze should have closed her first set against Venus Williams last night and saved some time. Because she should have.
But these arguments aside, it makes no sense to schedule any night match player for the early match the next day unless it is necessary, and it wasn't necessary today. Would a not-exhausted Chakvetadze have beaten Maria Sharapova? Maybe. But at least it would have been an interesting match, and the fans would have gotten their money's worth.
Final score: Maria Sharapova def. Anna Chakvetadze, 6-3, 6-2 (or, as someone on a tennis forum put it, San Diego Organizers def. Chakvetadze).