Lucas Arnold Ker
Lucas Arnold Ker is an Argentine former professional tennis player.
Arnold Ker started playing tennis in the Olivos Tenis Club of Buenos Aires, under coach Malcolm Campbell. He is the younger brother of Patricio Arnold. He is right-handed and turned professional in 1994. He played several times for the Argentine Davis Cup team, where he made his debut in 1997 against Venezuela. Arnold Ker was Roger Federer's opponent in the latter's first professional match in 1998, beating the 17-year-old future List of [ATP number 1 ranked singles tennis players|singles world No. 1] and 20-time major singles champion in straight sets. Arnold Ker retired from professional tennis in 2016.
Cancer
In August 2006, he was diagnosed with testicular cancer. The testicle was removed, and he successfully underwent chemotherapy. In 2008, he was in remission and returned to playing professional tennis.ATP Tour career finals
Doubles: 33 (15 titles, 18 runner-ups)
| Result | W–L | Date | Tournament | Tier | Surface | Partner | Opponents | Score | |||||||||||||||||||||||||||||
| Win | 1–0 | 1996 [Campionati Internazionali di San Marino – Doubles|] | San Marino, San Marino | World Series | Clay |  ATP Challenger and ITF Futures finalsSingles: 5 (2–3)
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dts|Aug 1997