Question: What sport did Justin Gimelstob and Olivier Rochus both play professionally?

Context paragraphs:
2005 China Open – Men's Doubles: Justin Gimelstob and Graydon Oliver were the defending champions, but Oliver did not participate this year.  Gimelstob partnered Nathan Healey and successfully defended his title.

2000 Nottingham Open – Doubles: Patrick Galbraith and Justin Gimelstob were the defending champions, but did not partner together this year.  Galbraith partnered Brian MacPhie, losing in the quarterfinals.  Gimelstob partnered Jared Palmer, losing in the first round.

1999 Nottingham Open – Doubles: Justin Gimelstob and Byron Talbot were the defending champions, but Talbot did not partner this year.  Gimelstob partnered Patrick Galbraith.

2000 Franklin Templeton Tennis Classic – Doubles: Justin Gimelstob and Richey Reneberg were the defending champions, but Gimelstob did not participate this year.  Reneberg partnered Jared Palmer, successfully defending his title.

1999 Legg Mason Tennis Classic – Doubles: Grant Stafford and Kevin Ullyett were the defending champions.  Stafford chose not to participate this year.  Ullyett partnered with Piet Norval but lost in the semifinals to the eventual champions Justin Gimelstob and Sébastien Lareau.  <BR>Justin Gimelstob and Sébastien Lareau won in the final over David Adams and John-Laffnie de Jager, 7–5, 7–6.

Justin Gimelstob: Justin Jeremy Gimelstob (born January 26, 1977) is a retired American tennis player.  Gimelstob has been a resident of Morristown, New Jersey, and as of 2009 lived in Santa Monica, California.

2001 Canada Masters – Doubles: 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.

Olivier Rochus: Olivier Rochus (] ; born 18 January 1981) is a retired Belgian tennis player.  He has won two singles titles in his career and in 2004 won the French Open doubles title partnering fellow Belgian Xavier Malisse.  Rochus' career-high singles ranking is World No. 24.

2001 Kroger St. Jude International – Doubles: Justin Gimelstob and Sébastien Lareau were the defending champions but only Gimelstob competed that year with Jared Palmer.

2006 China Open – Men's Doubles: Justin Gimelstob and Nathan Healey were the defending champions, but Gimelstob did not participate this year.  Healey partnered Ashley Fisher, losing in the first round.

Supporting paragraphs: Justin Gimelstob Olivier Rochus
Answer: tennis