"We have worked on a lot of things the week before hear and it's nice to seeing those things come to fruition in the matches."
Earlier Sitak and his Dutch partner Wesley Koolhof caused a big upset to reach the third round.
Sitak and Koolhof came from a set down to beat the 9th seeds Croatian Ivan Dodig and American Rajeev Ram 5-7, 7-5 6-4 in 2 hr 12.
Sitak and Koolhof had beaten Dodig and Ram earlier in the year in Montpellier but were still underdogs against a top ranked team.
The first set was tight but Sitak struggled to hold serve, saving a break point in his first service game and he was eventually broken in the 12th game to hand the Croatian / American combination the set.
Games went with serve until the 11th game of the second set when Sitak and Koolhof broke Dodig with the Kiwi making a back hand pass to break before Sitak served out the set.
Sitak is thrilled to reach the third round at Roland Garros for the first time.
"I am very tired because it was a long match played at a high level and we had a nice ten minute period in the middle of the match where we broke serve twice and then served out the match," Sitak said.
The Kiwi Dutch combination will meet either the unseeded Argentines Diego Schwartzman and Guido Pella or the 5th seeds Juan Sebastien Cabal and Robert Farah for a place in the quarter-finals.