Originally posted on 01/09/2013:
Let's do a little maths then. In decimal odds, for my brain's sake.
Serena has to play 7 games to win the tournament. She will typically play against 3 or 4 much weaker opponents that stands no chance except if she gets injured, 1 or 2 that can pull a miracle but are not very consistent (at AO, I'd say maybe Radwanska, Kvitova and a few others) and 1 or 2 more serious contenders (Azarenka, Na Li, Sharapova) that have a real chance but are still underdogs.
She will gets 1.1 (-1000) odds against the weak, 1.2 against the average (-500) and 1.4 against the elite (-250). Be aware I am generous with the odds, it is usually a bit lower on my book (bet365 UK).
If she plays 4 weaklings, 1 average and 2 elites, odds are 1.1^4 * 1.2 * 1.4^2 = 3.44 (+244).
Conclusion : IMHO you get a better payoff by playing game after game on Serena if you have decent odds in your book. If she barely finishes a game after getting injured, you can play it safely and keep your winning or edge on the opponent.