Mate Pavić and Michael Venus were the defending champions, but Venus chose to compete in Delray Beach instead.
 Pavić played alongside Alexander Peya, but lost in the quarterfinals to Robin Haase and Dominic Inglot.
Mate Pavić and Michael Venus were the defending champions, but Pavić chose to compete in Sofia instead.
 Venus played alongside Robert Lindstedt, but lost in the quarterfinals to Alexander and Mischa Zverev.
Nicolas Reissig (born 7 April 1989, in Oberndorf bei Salzburg) is an Austrian tennis player.
 Reissig has a career high ATP singles ranking of 344, achieved on 15 July 2013.
 Reissig made his ATP main draw doubles debut at the 2014 MercedesCup partnering Robin Kern, losing in the first round to Mate Pavić and André Sá.
 Reissig has a total of 7 singles titles and 4 doubles titles on the futures circuit.
Mate Pavić and Michael Venus were the defending champions, but Pavić chose to compete in Stuttgart instead.
 Venus played alongside André Sá, but lost to Łukasz Kubot and Marcelo Melo in the semifinals.
Mate Pavić and Michael Venus were the defending champions, but decided not to defend their title.
Mate Pavić and Michael Venus were the defending champions, but Pavić chose to compete in Sydney instead.
 Venus played alongside Robert Lindstedt, but lost in the first round to Nicholas Monroe and Artem Sitak.
George Morgan (born 7 February 1993) is a British tennis player.
 He won the Boys' Doubles title at the 2011 Wimbledon Championships alongside Mate Pavić.
Laura Siegemund and Mate Pavić were the defending champions, but Siegemund was unable to compete due to injury.
 Pavić played alongside Andreja Klepač, but lost to Alicja Rosolska and Santiago González in the first round.
Mate Pavić (born 4 July 1993) is a Croatian professional tennis player specialising in doubles.
 Mate won the 2016 US Open mixed doubles title in partnership with Laura Siegemund, and reached the 2017 Wimbledon Championships men's doubles finals partnering Oliver Marach.
Philip Clive Dent (born 14 February 1950), is a former professional tennis player.
 Dent's high water mark as a pro singles player was reaching the Australian Open final in 1974, which he lost to Jimmy Connors in four sets.
 Dent was also the Men's Doubles champion at the Australian Open in 1975 (with teammate John Alexander), and the Mixed Doubles champion at the US Open in 1976 (with teammate Billie Jean King).

Question: Are both Mate Pavić and Phil Dent tennis players specializing in doubles?
Answer: no