Meanwhile Nadal smoothly negotiated the potential stumbling block presented by Paire, launching his bid for a 10th French Open trophy with a largely routine 6-1 6-4 6-1 win.
Back on the court where he completed his career Grand Slam, Novak Djokovic showed no sign of the crisis of confidence that has affected his game since winning the French Open previous year.
Paris: Novak Djokovic began his partnership with Andre Agassi with victory on Monday but the American legend definitely won't be around if the Serb successfully defends his title.
There was never any real danger of Djokovic being upset in the first round of a grand slam for the first time since the 2006 Australian Open - Granollers, who likes a grunt or two, had won a combined 10 games in their three prior encounters - yet Djokovic needed nine set points to put away the Spaniard in the second set.
Djokovic progressed 6-3 6-4 6-2 in Paris and will next face Portugal's Joao Sousa, who defeated Janko Tipsarevic 4-6 7-6 6-2 6-2.
Nadal's last French Open title came in 2014.
In the opening and deciding sets, Paire had no reply for Nadal's groundstrokes and overall strong game.
- The match was halted on Monday due to poor light and rain and play resumed on Tuesday with the scores tied at a set apiece.
"If I feel fresh and energized and excited to play for a week", he said, "that's when I do my best".
Channelling the confidence built up during a 17-match winning streak in taking claycourt titles in Monte Carlo, Barcelona and Madrid, Nadal then pulled clear as Paire suffered a reaction to taking energy tablets.
"For me, it's important to serve a little bit better than what I did today", Nadal told reporters at a post-match press conference.
"He has a lot to share with me outside and inside of the tennis lines, I'm really enjoying it so far", Djokovic said about 1999 French Open victor Agassi afterwards. "No matter whom I play it's going to be hard".
Roberto Bautista, seeded 17th, also moved to the second round after beating Australian John Millman 6-2, 6-2, 0-6, 6-1.
Tomljanovic saved two match points on her serve to take the game to deuce but Bertens sealed the match when her opponent hit a forehand long.
Despite the defeat, Fourlis walked off to a standing ovation.
He beat France's Benoit Paire 6-1, 6-4, 6-1 with consummate ease.
Although Muguruza's first-strike tennis proved too much for the 36-year-old Italian as she beat her 6-2, 6-4, the Spaniard was full of admiration afterwards. The fourth-seeded Spanish player takes on 2010 champion Francesca Schiavone in an intriguing matchup.