Bob and Mike Bryan were the two-time defending champions, but lost in the semifinals to Pierre-Hugues Herbert and Nicolas Mahut.
Vasek Pospisil and Jack Sock were the defending champions, but lost in the final to Pierre-Hugues Herbert and Nicolas Mahut, 3–6, 6–7.
Pierre-Hugues Herbert and Nicolas Mahut were the defending champions, but lost in the second round to Novak Djokovic and Viktor Troicki.
Pierre-Hugues Herbert and Nicolas Mahut were the defending champions, but withdrew before their second round match due to Herbert's leg injury.
Nicolas Mahut and Vasek Pospisil were the defending champions, but Pospisil chose not to participate this year.
 Mahut played alongside Pierre-Hugues Herbert, but lost in the semifinals to Ivan Dodig and Marcel Granollers.
Jan-Michael Gambill and Travis Parrott were the defending champions, but Gambill did not participate this year.
 Parrott partnered Robby Ginepri, losing in the first round.
Travis Parrott (born August 16, 1980 in Portland, Oregon) is an American professional ATP tennis doubles player.
 He is primarily a doubles specialist.
 Travis is the son of Brian Parrott, a pro tennis organizer who helped bring a pair of Davis Cup events to Portland in the 1980s.
Pierre-Hugues Herbert was the defending champion but withdrew before the tournament began.
Pierre-Hugues Herbert and Albano Olivetti were the defending champions but only Olivetti chose to defend his title, partnering Kevin Krawietz.
 Olivetti lost in the first round to Roman Jebavý and Igor Zelenay.
Pierre-Hugues Herbert (] ; born 18 March 1991) is a French professional tennis player.
 In doubles, he won the title at the 2015 US Open and 2016 Wimbledon as well as several Masters 1000 tournaments along with Nicolas Mahut.
 In singles he has reached one ATP career final (at the 2015 Winston-Salem Open), and achieved his career high singles ranking of World No. 64 on 14 August 2017.

Question: who had more success as singles, Travis Parrott or Pierre-Hugues Herbert
Answer: Pierre-Hugues Herbert