Question: Scott Lipsky and Donald Johnson, have which mutual occupation?

Context paragraphs:
Donald Johnson: Donald James "Don" Johnson (born September 9, 1968) is a former professional tennis player from the United States who reached the World No. 1 doubles ranking in 2002.  Although born in Bethlehem, Pennsylvania, he was raised and learned the sport of tennis in the Pittsburgh suburb of Mt. Lebanon, Pennsylvania.  Johnson attended Fairview High School in Erie, Pennsylvania, and won the PIAA State Singles Championship in 1984.  During his career, he won the Wimbledon men's doubles title in 2001 (partnering Jared Palmer), and the Wimbledon mixed doubles title in 2000 (partnering Kimberly Po).  He also won the doubles title at the Tennis Masters Cup in 2000 (partnering Piet Norval).  He won a total of 23 top-level doubles titles.

2013 Internazionali BNL d'Italia – Men's Doubles: Marcel Granollers and Marc López were the defending champions, but lost to Santiago González and Scott Lipsky in the quarterfinals. <br>

2011 Bauer Watertechnology Cup – Doubles: Scott Lipsky and Rajeev Ram were the defending champions but Lipsky decided not to participate. <br>

2010 Tallahassee Tennis Challenger – Doubles: Eric Butorac and Scott Lipsky were the defending champions, but Butorac chose to participate in Barcelona instead.Lipsky partnered up with David Martin, but they lost in the first round against Robert Kendrick and Bobby Reynolds. Stephen Huss and Joseph Sirianni won in the final 6–2, 6–4 against Robert Kendrick and Bobby Reynolds

Scott Lipsky: Scott Lipsky (born August 14, 1981, in Merrick, New York) is a professional tennis player from the United States.  He is primarily a doubles specialist.

2017 Estoril Open – Doubles: Eric Butorac and Scott Lipsky were the defending champions, but Butorac retired from professional tennis in September 2016 and Lipsky chose to compete in Istanbul instead.

2011 Atlanta Tennis Championships – Doubles: Scott Lipsky and Rajeev Ram were the defending champions, but were defeated in the first round by wildcards Drake Bernstein and Kevin King. <br>

2015 Irving Tennis Classic – Doubles: Santiago González and Scott Lipsky were the defending champions, but González did not participate.  Lipsky partnered with Treat Huey, but lost in the quarterfinals to Pablo Andújar and Diego Schwartzman.

2016 Estoril Open – Doubles: Treat Huey and Scott Lipsky were the defending champions, but chose not to compete together.  Huey played alongside Max Mirnyi, but lost in the semifinals to Eric Butorac and Lipsky. <br>

2012 French Open – Mixed Doubles: Casey Dellacqua and Scott Lipsky were the defending champions.  Dellacqua chose not to participate this year while Lipsky partnered with Vladimíra Uhlířová, but they were defeated in the first round by Virginie Razzano and Nicolas Devilder. <br>

Supporting paragraphs: Scott Lipsky Donald Johnson
Answer: professional tennis player