Elizabeth Smylie (née Sayers, born 11 April 1963), sometimes known as Liz Smylie, is a retired Australian professional tennis player.
 During her career, she won four Grand Slam titles, one of them in women's doubles and three in mixed doubles.
 She also won three singles titles and 36 doubles titles.
American tennis player Pancho Gonzales had a long-running rivalry with Australian Ken Rosewall.
 Gonzales is still sometimes considered to be a candidate for the greatest tennis player of all time; he was the dominant player of the 1950s and still holds the men's all-time record of being ranked world No. 1 for eight years.
 Rosewall became the world's best player upon Gonzales's semi-retirement in 1961 and held that position either by himself or sharing it with others for six years.
 Rosewall was signed in 1956 by the promoter Jack Kramer, a former #1 player himself, to join his small band of touring professionals in 1957.
 He then engaged in a round-the-world, head-to-head tour against Gonzales, the defending world's champion, over the next five months, winning 26 matches but losing 50.
 In his 1979 autobiography Kramer included both Gonzales and Rosewall in his list of the 21 greatest players of all time.
 Kramer, however, initially "panicked" upon signing Rosewall.He was a cute little fellow with a dink serve, who operated mostly from the baseline.
 That great volley of his hadn't been developed yet.
 I was afraid that Gorgo would eat him alive and put us out of business the rest of the way.
 But like a lot of people I completely underestimated Rosewall.
 Before their opening match in Melbourne, Kramer went to Gonzales and asked him to "carry" Rosewall, giving him a better share of the gate to gain his assent.
 Gonzales did try to carry out his part of the deal for a few matches, but then called it off, telling Kramer that he was no longer able to play his normal game.
 Kramer agreed.
 "It was... obvious that Rosewall was not the pushover I had feared.
 (In fact, Gonzales only beat him 50–26, and it was always competitive.)"
 Six years older than Rosewall, 13 years later, in 1970, Gonzales defeated him in 6–4, 6–4, in the 199th and next-to-last match they ever played—Gonzales was 42 years old at the time and Rosewall was considered to be the co-No.
 1 player in the world.
Jana Novotná and Helena Suková successfully defended their Wimbledon title after defeating Kathy Jordan and Elizabeth Smylie 6–4, 6–1 in the final.
Janko Tipsarević (, ] ; born 22 June 1984) is a Serbian professional tennis player.
 His career-high singles ranking is world No. 8, achieved on 2 April 2012.
 In his career, he has won four ATP World Tour titles, one ATP doubles title, three Futures, and 15 Challenger titles.
 Tipsarević also won the 2001 Australian Open Junior title.
 Tipsarević has achieved two victories over a World No. 1 player, having defeated compatriot Novak Djokovic twice.
 He also has thirteen victories against other players in the top 10: four wins against Tomáš Berdych, and one each against Fernando González, Mikhail Youzhny, David Ferrer, James Blake, Gaël Monfils, Andy Murray and Juan Mónaco.
 He holds victories over former World No. 1 players Carlos Moyá, Marat Safin, Lleyton Hewitt, Juan Carlos Ferrero and Andy Roddick.
 His best results at a Grand Slam have been reaching the quarterfinals at the US Open in 2011 and 2012.
 He is only the second Serb to reach the final 16 at all four different grand slams.
Peter Christian Cain (born 20 November 1958) is an Australian pair skater who currently works as a coach.
 With sister Elizabeth Cain, he is the 1976 World Junior bronze medalist and a four-time Australian national champion.
 Their highest placement at the World Championships was 12th in 1977.
 They competed in the 1980 Winter Olympics, finishing eleventh.
 He is the uncle and former coach of Australian national champion Sean Carlow and father of American skater Ashley Cain.
 He also coaches Alexei Krasnozhon and Brooklee Han.
 He currently works as a coach in the Euless, Texas area.
Juan Carlos Ferrero Donat (] ; born 12 February 1980) is a retired professional tennis player, and a former world No. 1 player, from Spain.
 He captured the men's singles title at the 2003 French Open, and in September of that year, became the 21st player to hold the world No. 1 ranking.
 He was also the runner-up at the 2002 French Open and the 2003 US Open.
 His nickname is "Mosquito" due to his speed and his slight physical build.
 Ferrero retired from the game after the 2012 Valencia Open 500.
Kenneth Robert Rosewall {'1': ", '2': ", '3': 'AM, MBE', '4': "} (born 2 November 1934) is a former world top-ranking amateur and professional tennis player from Australia.
 He won a record 23 tennis Majors including 8 Grand Slam singles titles and before the Open Era a record 15 Pro Slam titles and a record 35 Major finals overall.
 He won the Pro Grand Slam in 1963.
 Rosewall won 9 slams in doubles with a career double grand slam.
 He is considered to be one of the greatest tennis players of all time.
 He had a renowned backhand and enjoyed a long career at the highest levels from the early 1950s to the early 1970s.
 Rosewall was one of the two best male players for about nine years and was the World No. 1 player for a number of years in the early 1960s.
 He was ranked among the top 20 players, amateur or professional, every year from 1952 through 1977.
 Rosewall is the only player to have simultaneously held Pro Grand Slam titles on three different surfaces (1962–1963).
 At the 1971 Australian Open he became the first male player during the open era to win a Grand Slam tournament without dropping a set.
Stephen L. "Steve" Wilkinson ((1941--) 29, 1941 – (2015--) 21, 2015 ) was an American tennis player and tennis coach.
 As the head coach of Gustavus Adolphus College men's tennis team from 1971 till 2009, Wilkinson was the coach with most wins in the history of collegiate men’s tennis (929).
 He was also the No. 1 player in the United States in the 45-, 50-, 55-, and 60-and-over age groups, represented the US team in Dubler Cup, Perry Cup and Austria Cup and was a world team champion in 1989 (Uruguay) and word silver medalist 1992 (Germany).
 Wilkinson was inducted into United States Professional Tennis Association’s Hall of Fame, the USTA Missouri Valley Hall of Fame and the ITA Men’s Collegiate Tennis Hall of Fame.
Paul Annacone (born March 20, 1963) is an American former touring professional tennis player and current tennis coach.
 He is the former coach of open-era leader in Grand Slams Roger Federer and former World No. 1 Pete Sampras.
 Annacone is currently a coach at ProTennisCoach.com and a commentator at Tennis Channel
Roger Federer won the Australian Open, beating Briton Andy Murray, whom he also beat in the final of the 2008 US Open.
 Federer played in eighteen tournaments in 2010, and won five.
 He made the semifinals of his opening tournament at the Qatar Open in Doha, losing to Nikolay Davydenko, and at the Estoril Open, which he had won in 2008, losing to defending and eventual champion Albert Montañés.
 Federer was runner-up in the Mutua Madrileña Madrid Open to Rafael Nadal.
 At the French Open, he faced his opponent in the previous year's final, Robin Söderling at the quarterfinals stage and lost.
 As defending champion at Wimbledon, he was defeated in the quarterfinals by Tomáš Berdych in four sets, thus ending his streak of seven consecutive Wimbledon finals also falling to world no. 3, his lowest ranking since 2003.
 During the summer hard-court season, Federer hired Paul Annacone to be his coach and revive his form.
 At the 2010 US Open, Federer advanced to his seventh straight semifinal appearance, but lost to Novak Djokovic in five sets, despite holding two match points in the final set.
 Federer's ranking slipped from no. 2 to no. 3 after the tournament, but he finished the year strong with victories in Stockholm, Basel, and the ATP Tour Finals to pass Djokovic in the rankings and finish the year at no. 2.

Question: Who is a former coach of a World No. 1 player, Elizabeth Smylie or Paul Annacone?
Answer: Paul Annacone