Robert Lindstedt and Nenad Zimonjić were the defending champions but decided not to participate together.
 Lindstedt played alongside Łukasz Kubot, but lost in the first round to Julien Benneteau and Édouard Roger-Vasselin.
 Zimonjić teamed up with Daniel Nestor, but lost in the quarterfinals to Michaël Llodra and Nicolas Mahut.
Max Mirnyi and Nenad Zimonjić were the defending champions, but did not participate together this year.
 Mirnyi partnered Mark Knowles, losing in the semifinals.
 Zimonjić partnered Brian MacPhie and successfully defended his title.
Goran Ivanišević (; born 13 September 1971) is a retired Croatian professional tennis player and current tennis coach.
 He is the only person to win the men's singles title at Wimbledon as a wildcard.
 He achieved this in 2001, having previously been runner-up at the championships in 1992, 1994 and 1998.
 Before the 2001 tournament, he was ranked 125th and after his victory he was 16th.
 His career-high singles ranking was World No. 2 (behind Pete Sampras) in 1994.
 He coached Marin Čilić from September 2013 to July 2016, leading Čilić to his biggest achievement to date, the 2014 US Open title.
Nenad Zimonjić (Serbian Cyrillic: , ] ; born June 4, 1976) is a Serbian professional tennis player who was ranked World No. 1 in 2008 in doubles.
 He is the second tennis doubles player from Serbia to hold the World No. 1, after Slobodan Živojinović.
 While Zimonjić is known as a doubles specialist (winning 3 Grand Slams in men's doubles and 5 in mixed doubles), he has recorded two big wins in his singles career.
 A 22 year span consisting of 54 Davis Cup ties including 43 victories has resulted in him becoming the most accomplished Davis Cup player in his nations history.
 His strongest weapon is very powerful first serve that he can hit at up to 235 km/h (146 mph).
Sun Tiantian and Nenad Zimonjić were the defending champions, but Sun chose not to participate, and only Zimonjić competed that year.
 Zimonjić partnered with Anna-Lena Grönefeld, but lost in the first round to Cara Black and Leander Paes.
Slobodan "Boba" Živojinović (, ] ; born on July 23, 1963) is a retired Serbian tennis player who competed for SFR Yugoslavia.
 Together with Nenad Zimonjić he is the only tennis player from Serbia to be the World No. 1 in doubles.
 As a singles player, he reached the semi-finals of the 1985 Australian Open and the 1986 Wimbledon Championships, achieving a career-high ranking of World No. 19.
Daniel Nestor and Nenad Zimonjić were the defending champions, but they split in 2011.
 Daniel Nestor qualified with his new partner Max Mirnyi and Nenad Zimonjić with Michaël Llodra.
Daniel Nestor and Nenad Zimonjić were the defending champions, but decided not to participate together.
 Nestor partnered Max Mirnyi, while Zimonjić teamed up with Michaël Llodra.
 Mirnyi and Nestor defeated Zimonjić and Llodra in the semifinals, 7–6, 7–6.
 In the final, they won against Juan Sebastián Cabal and Eduardo Schwank 7–6, 3–6, 6–4 for their first Grand Slam doubles title as a team.
The 2011 ATP World Tour Finals (also known as the 2011 Barclays ATP World Tour Finals for sponsorship reasons) was a tennis tournament that was played at the O Arena in London, United Kingdom between 20 and 27 November 2011.
 The defending champion in singles was world no. 4 Roger Federer, while the defending champions in doubles were Daniel Nestor and Nenad Zimonjić.
 However, they did not defend their title together as they separated after the 2010 event.
 Zimonjic formed a team with Michaël Llodra for the season, and Nestor partnered with Max Mirnyi.
 Federer successfully defended his crown, winning an unprecedented sixth title, while Nestor and Mirnyi captured the doubles title.
Daniel Nestor and Nenad Zimonjić were the defending champions but Zimonjić decided not to participate.
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Question: Who has achieved a higher World Ranking (in either singles or doubles), Goran Ivanišević or Nenad Zimonjić?
Answer: Nenad Zimonjić