Question: Which tennis player also became a coach, Sébastien Lareau or Martina Navratilova?
Context: Unmatched is a documentary about tennis players Martina Navratilova and Chris Evert, their decades-long on-court rivalry and lifelong friendship, created for ESPN's "30 for 30" documentary series.  Evert and Navratilova met in 80 matches, 60 finals and 14 grand slam finals with Navratilova sporting a 43-37 advantage. Sébastien Lareau (born April 27, 1973 in Montreal, Quebec) is a retired professional tennis player.  He became the first Canadian to win a Grand Slam title by winning the 1999 U.S. Open Men's Doubles with his American partner Alex O'Brien. Martina Navratilova (Czech: "Martina Navrátilová" ] ; born Martina Šubertová ] ; October 18, 1956) is a former Czechoslovak and later American tennis player and coach.  In 2005, "Tennis" magazine selected her as the greatest female tennis player for the years 1965 through 2005 and she is considered one of the best, if not the best, female tennis players of all time. Gisela Dulko (] ; born 30 January 1985, in Tigre) is a retired professional tennis player from Argentina.  Although she enjoyed modest success in singles, reaching world no. 26 and winning four WTA Tour titles, her speciality was doubles, where she achieved a world no. 1 ranking.  Partnering with Flavia Pennetta, Dulko won the 2010 WTA Tour Championships and the 2011 Australian Open in doubles.  Dulko also reached the mixed doubles final at the 2011 US Open, with Edward Schwank.  She is remembered for her ability to upset the big names on the tour, such as Maria Sharapova in the second round of Wimbledon in 2009; and Samantha Stosur in the third round of Roland Garros in 2011.  She also beat Martina Navratilova in the second round of Wimbledon in 2004 in Navratilova's final Grand Slam singles match. Maria Fernanda Barbato Alves (born 17 April 1983), also known as Nanda Alves, is a Brazilian tennis player.  She is currently coached by her father Carlos and former tennis player Thomaz Koch.  As of 1 March 2010, Alves is ranked World No. 262, and is the highest ranked Brazilian player.  She has enjoyed success at the ITF Circuit, winning 18 singles and 26 doubles titles so far.  Alves made her WTA Tour debut at Copa Colsanitas in 2004, and has played qualifications for all four Grand Slam events.  Partnering with Vanessa Henke, Alves took part in the 2005 Australian Open doubles event, but they lost to Daniela Hantuchová and Martina Navratilova in the first round. Judy Hill Nelson is an American author best known for her 1983–1991 romance (while married) with and eventual palimony suit against women's tennis star Martina Navratilova.  After their break-up, Nelson was the author of the books "Love Match: Nelson vs. Navratilova", chronicling her relationship with the tennis star, and "Choices: My Journey After Leaving My Husband for Martina and a Lesbian Life", chronicling her coming out as a lesbian in the mid-1980s.  She is the mother of two sons. The 2001 Canada Masters – Doubles was the men's doubles event of the one hundred and twelfth edition of the Canada Masters; a WTA Tier I tournament and the most prestigious men's tennis tournament held in Canada.  Sébastien Lareau and Daniel Nestor were the defending champions but they competed with different partners that year, Lareau with Justin Gimelstob and Nestor with Sandon Stolle.  Gimelstob and Lareau lost in the first round to Mark Knowles and Brian MacPhie, as did Nestor and Stolle to Jan-Michael Gambill and Simon Larose.  Jiří Novák and David Rikl won in the final 6–4, 3–6, 6–3 against Donald Johnson and Jared Palmer. Meredith McGrath (born April 28, 1971) is a former professional tennis player.  She was born in Midland, Michigan, USA and made her debut on the Women's Tennis Association tour in 1988.  In her eight-year professional career Meredith achieved career-high world rankings of #18 in singles and #4 in doubles.  She notched victories over such players as Martina Navratilova, Martina Hingis, Anna Kournikova, Jana Novotna, Arantxa Sanchez Vicario, and Gigi Fernandez.  The pinnacle of her career came in reaching the singles semi-finals and doubles finals at the 1996 Wimbledon Championships.  In the singles she defeated Mana Endo, Amanda Coetzer, Nancy Feber, Katarína Studeníková and Mary Joe Fernandez before losing to Arantxa Sánchez Vicario.  An injury the week prior to the 1996 Wimbledon Championships eventually ended her career.  Meredith won the 1995 U.S. Open Mixed Doubles Championship (she was runner-up in 1989) and was the runner-up in the 1994 Australian Open Doubles Championship.  Meredith won three WTA singles titles: Oklahoma City and Eastbourne in 1994 and Birmingham in 1996, 25 doubles titles.  She retired with a 140–83 record in singles and a 189–40 record in doubles.  Meredith was recognized by Tennis Magazine as the WTA Comeback Player of the Year as she overcame near career-ending injuries to having her most successful competitive season in 1996.  In 1994 she received the WTA Tour Comeback Player of the Year. The 2000 du Maurier Open – Men's Doubles was the men's doubles event of the one hundred and eleventh edition of the Canadian Open; a WTA Tier I tournament and the most prestigious men's tennis tournament held in Canada.  Jonas Björkman and Patrick Rafter were the defending champions, but Rafter chose not to participate, and only Bjorkman competed that year.  Bjorkman partnered with Max Mirnyi, but lost in the semifinals to Joshua Eagle and Andrew Florent.  Sébastien Lareau and Daniel Nestor won in the final 6–3, 7–6(3), against Joshua Eagle and Andrew Florent. Roy Stanley Emerson (born 3 November 1936) is an Australian former World number one tennis player who won 12 Major singles titles and 16 Grand Slam tournament men's doubles titles.  He is the only male player to have completed a Career Grand Slam (winning titles at all four Grand Slam events) in both singles and doubles.  His 28 major titles are an all-time record for a male amateur player.  Emerson is the first male player to win each amateur major title at least twice in his career.  He is one of only eight men to win all four majors in his career.  He was the first male player to win 12 majors.  Along with Novak Djokovic, he is one of only two male players to win six Australian Championships.  He won five of them consecutively (1963–67).  His 12 wins have since been surpassed.  Emerson is one of only five tennis players all-time to win multiple slam sets in two disciplines, only matched by Margaret Court, Martina Navratilova, Frank Sedgman and Serena Williams.
Answer: Martina Navratilova