Question: Which player was a better tennis player with his non-dominant hand, Jürgen Melzer or Albert Costa?

Context paragraphs:
2012 Australian Open – Day-by-day summaries: In Men's Singles, on the opening day, play began with Local hope Bernard Tomic struggling in the beginning two sets but later working hard in the next three sets, defeating Spaniard Fernando Verdasco.  Juan Martín del Potro also had to earn victory by losing the first set but later winning the next three sets defeating Adrian Mannarino.  Meanwhile, Rafael Nadal overcomes Alex Kuznetsov.  Spaniard Pere Riba had to defeat compatriot Albert Montañés whereas Ukrainian Sergiy Stakhovsky had to defeat his compatriot Illya Marchenko to advance to the second round.  Florent Serra advanced to the second round after Steve Darcis was forced to retire in the third set, leading two sets to love, because of leg cramps.  Other seeds such as Tomáš Berdych, Mardy Fish, Nicolás Almagro, Alexandr Dolgopolov, John Isner, Stanislas Wawrinka and Kevin Anderson along with Marcos Baghdatis, Olivier Rochus, Tommy Haas, Andreas Beck and Grigor Dimitrov all progressed comfortably into the second round while Juan Mónaco, Ivan Ljubičić and Jürgen Melzer were sent crashing out in the first round.  In the evening, Roger beats Alexander Kudryavtsev in three straight tiebreakers and David Nalbandian advanced to the second round after Jarkko Nieminen was forced to retire in the second set because of stomach cramps.

Iveta Benešová: Iveta Benešová (] ) (formerly Melzer, Czech: Melzerová ; born 1 February 1983) is a Czech former professional tennis player.  She began playing tennis at age of 7 and turned professional in 1998 in Prague.  She has won two WTA Tour events and one Grand Slam in mixed doubles partnering with Jürgen Melzer at the 2011 Wimbledon Championships.  On 14 September 2012 she married Jürgen Melzer and adopted his family name.  She announced her retirement from professional tennis via her Facebook page 13/08/2014.  In 2015, she divorced Melzer and reverted to using her maiden name.

Julian Knowle: Julian Knowle (born 29 April 1974) is an Austrian male professional tennis player.  Being a born left-hander, Knowle is now one of the few on the ATP Tour who plays his forehand, backhand, and even volleys double-handed.  He was Austria's most successful doubles player in history by reaching world no. 6 in the ATP doubles rankings in January 2008, before being matched by Jürgen Melzer, who reached no. 6 in September 2010, and overtaken by Alexander Peya, who reached no. 3 in August 2013.

Karim Alami: Karim Alami (Arabic: كريم علمي‎ ‎ ) (born 24 May 1973) is a retired tennis player from Morocco, who turned professional in 1990.  The right-hander won two career titles in singles, both in 1996 (Atlanta and Palermo), and reached a career-high ATP singles ranking of World No. 25 in February 2000.  Alami reached the semifinals of the 2000 Monte Carlo Masters, defeating Magnus Norman and Albert Costa en route.

Marc-Kevin Goellner: Marc-Kevin Peter Goellner (born 22 September 1970) is a former professional tennis player from Germany.  He won two singles titles, achieved a Bronze medal in doubles at the 1996 Summer Olympics and attained a career-high singles ranking of World No. 26 in April 1994.  Goellner reached the quarterfinals of the 1997 Rome Masters, defeating top tenners Richard Krajicek and Albert Costa en route.

Artificial harmonic: To produce an artificial harmonic, a stringed instrument player holds down a note on the neck with one finger of the non-dominant hand (thereby shortening the vibrational length of the string) and uses another finger to lightly touch a point on the string that is an integer divisor of its vibrational length, and plucks or bows the side of the string that is closer to the bridge.  This technique is used to produce harmonic tones that are otherwise inaccessible on the instrument.  To guitar players, one variety of this technique is known as a pinch harmonic.

Jürgen Melzer: Jürgen Melzer (born 22 May 1981 in Vienna) is an Austrian tennis player.  He reached a career-high singles ranking of world No. 8 in April 2011, and a doubles ranking of world No. 6 in September 2010.  He is a left-handed tennis player, but is right-handed in everyday life.  He has a younger brother, Gerald Melzer, with whom he has played doubles in several tournaments.

Albert Costa: Costa began playing tennis at the age of five.  He first came to the tennis world's attention as an outstanding junior player.  In 1993, he reached the French Open junior final and won the Orange Bowl.  He turned professional later that year and quickly established a reputation as a strong clay court player.  Spanish former player and commentator for Spanish television Andrés Gimeno used to call him "the man with two forehands", because he could hit with the same accuracy and strength both forehand and backhand.  In 1994, he won two challenger series events and was named the ATP's Newcomer of the Year.

2013 Wimbledon Championships – Men's Singles: Roger Federer was the defending champion but lost in the second round to World No. 116 Sergiy Stakhovsky in a huge upset.  Stakhovsky was unable to build on his effort and lost in the next round in 4 sets to Jürgen Melzer.  Federer's loss marked the first time since the 2004 French Open, when he lost to Gustavo Kuerten in the third round, that he had failed to reach at least the quarterfinals in a Grand Slam event.  It was also Federer's earliest exit in this tournament since 2002, and the first time that Federer lost to a player ranked lower than 100 since his loss to then World No. 101 Richard Gasquet at the 2005 Monte Carlo Masters.

Albert Costa career statistics: This is an "(incomplete)" list of main career statistics page of Spanish professional tennis player Albert Costa.

Supporting paragraphs: Jürgen Melzer Albert Costa
Answer: Jürgen Melzer