Question: Which tennis player has retired, Hank Pfister or Maria Sharapova?
Context: Rossana de los Ríos (born 16 September 1975) is a retired professional tennis player from Paraguay.  She was born in the Paraguayan capital, Asunción, and now lives in Miami, USA, with her daughter Ana Paula Neffa de los Ríos and her husband Gustavo Neffa, a retired Paraguayan Association football player who played for Boca Juniors.  Rossana achieved a career high singles ranking of No. 51 on 12 September 2001, and No. 52 in doubles on the Sony Ericsson WTA Tour.  De los Ríos played doubles with Grand Slam champions such as Maria Sharapova, Svetlana Kuznetsova, Arantxa Sánchez Vicario, as well as Jelena Janković and Dinara Safina.  Rossana is also a former world number one Junior player, having won the 1992 Roland Garros Juniors event.  De los Ríos participated in six editions (1994, 2001, 2002, 2003, 2009 and 2010) of the Australian Open.  She was the only female tennis representative for Paraguay in the 1992 and 2000 Olympic Games. This is a list of the main career statistics of professional Russian tennis player, Maria Sharapova.  To date, Sharapova has won thirty five WTA singles titles including five Grand Slams, one year-ending championship, six WTA Tier I singles titles, three WTA Premier Mandatory singles titles and five WTA Premier 5 singles titles.  She was also the silver medallist in singles at the 2012 London Olympics. The 2014 Maria Sharapova tennis season officially began on 30 December 2013 with the start of the 2014 WTA Tour.  Sharapova began the season, having only played one match since the previous June due to a shoulder injury, at the Brisbane International.  After failing to defend her points during the winter and spring hard court season, Sharapova almost dropped out of the Top 10.  She rebounded by dominating the clay court season which saw her win Stuttgart, Madrid and the French Open.  Her only loss on clay came to a resurgent Ana Ivanovic.  She then won her first hard court title since the 2013 BNP Paribas Open at the China Open.  Her season ended on 24 October 2014 following her elimination from the round robin stage at the 2014 WTA Finals in Singapore.  She ended the year raned No. 2 behind Serena Williams. The 2012 Maria Sharapova tennis season officially began on 16 January 2012 with the start of the 2012 Australian Open.  Sharapova began the season ranked the number 4 player in the world. Marta Domachowska (; born 16 January 1986 in Warsaw) is a Polish retired professional tennis player ranked World No. 37 in singles (2006) and World No. 62 in doubles (2006).  She reached 2008 Australian Open fourth round in singles and won 2006 Canberra International in doubles with Roberta Vinci.  She also reached three WTA Tour singles finals at 2004 Hansol Korea Open (lost to Maria Sharapova), 2005 Internationaux de Strasbourg (lost to Anabel Medina Garrigues) and 2006 U.S. National Indoor Tennis Championships (lost to Sofia Arvidsson).  She was 2003 Australian Open finalist in girls' singles, represented Poland at the 2008 Summer Olympics and was member of Poland Fed Cup team.  Domachowska was the best female Polish tennis player after Magdalena Grzybowska's retirement and before Agnieszka Radwańska's successes. 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. Hank Pfister (born October 9, 1953) is a former tennis player from the United States, who won two singles titles (1981, Maui and 1982, Newport) during his professional career.  The right-hander reached his highest individual ranking on the ATP Tour on May 2, 1983, when he became World No. 19. Tatiana Golovin (Russian: Татья́на Григорьевна Голови́на , "Tatyana Grigoryevna Golovina" ; born 25 January 1988) is a Russian-born French retired professional tennis player.  She won the 2004 French Open mixed doubles event with Richard Gasquet, and reached the singles quarterfinal at the 2006 US Open, losing to the eventual champion Maria Sharapova.  Her highest singles ranking to date is 12.  In 2008, she was diagnosed with lower back inflammation and was forced to stop playing competitive tennis indefinitely. Maria Yuryevna Sharapova (Russian: Мари́я Ю́рьевна Шара́пова ; ] ; born April 19, 1987) is a Russian professional tennis player.  A United States resident since 1994, Sharapova has competed on the WTA tour since 2001.  She has been ranked world No. 1 in singles by the WTA on five separate occasions, for a total of 21 weeks.  She is one of ten women, and the only Russian, to hold the career Grand Slam.  She is also an Olympic medalist, having earned silver for Russia in women's singles at the 2012 Summer Olympics in London. Oleksandr "Alex" Kuznetsov (born February 5, 1987) is a retired American professional tennis player.  He currently works as the main hitting partner of Maria Sharapova.
Answer: Hank Pfister