(CNN) -- Defending champion Serena Williams will miss the Australian Open in January to give herself more time to recover from foot surgery.

The former world number one has not played competitively since winning her fourth Wimbledon crown in July.

She sustained the original injury after standing on broken glass at a restaurant shortly after winning her second grand slam of the year and 13th of her glittering career.

Williams attempted to come back ahead of the season-ending WTA Championships in Qatar, but had to abandon her attempts after aggravating the injury in training.

The American was also due to compete in the Hopman Cup in Australia next month, but in a statement released Thursday said she had been left with no choice but to pull out.

She said: "As I continue to rehabilitate my foot after the second surgery last month, it is with the utmost regret that I am withdrawing from the Hopman Cup and the 2011 Australian Open Championships.

"As I recently learned, pushing myself back into my intense training too early only caused me further injury and damage.

"While I desperately want to be back on the court and competing in the first grand slam tournament of the year, it is imperative for my health that I continue to work with my doctors to ensure my foot heals properly."

Williams dominated the early part of the 2010 season, with victories at the Australian Open and the grass of Wimbledon, but in her absence Caroline Wozniacki of Denmark claimed top spot in the global rankings.

Answer this series of questions:

1. How many Wimbledon crowns has Serena won?
2. When did she win the last one?
3. Is she going to be in the Aussie's open in January?
4. Why not?
5. From what?
6. How did she originally injure her foot?
7. Where?
8. What had she just won?
9. What win of her career was that?
10. What nationality is she?
11. What was she scheduled to compete in next month?
12. Did she have any choice but to pull out?
13. How much regret did she have about it?
14. What did she recently learn?
15. What source is this article from?
16. What year of Open Championships won't she be in now?
17. Who is she working with to ensure her foot heals properly?
18. Who claimed the top spot when Williams was absent?
19. Where's she from?
20. Are the rankings for the whole world?
21. Is Williams going to intensely train earlier or later now?

Numbered answers:
1. Four
2. July
3. No
4. To give herself more time to recover
5. From foot surgery
6. Standing on broken glass
7. Restaurant
8. Grand slam of the year
9. 13th
10. American
11. Hopman Cup
12. No
13. Utmost
14. "Pushing myself back into my intense training too early only caused me further injury and damage."
15. In a statement released Thursday
16. 2011
17. Her doctors
18. Caroline Wozniacki
19. Denmark
20. Yes
21. Later