The World No. 1 had been two sets up but 0-3 down in the third when rain caused the tie to be suspended late Monday. He quickly levelled at 3-3 on Tuesday and saved four break points in the eighth game before saving four set points.
Simona Halep converted her fifth match point to win her 14th straight match in Madrid and stay on track for a third consecutive title in the Spanish capital.
There was the usual pre-toss skipping routine, an abundance of shrieks and the oft-seen mid-match wobble as Maria Sharapova returned to the French Open following a two-year hiatus with a 6-1 4-6 6-3 win against Richel Hogenkamp on Tuesday.
In women's play, two-time Grand Slam victor Garbine Muguruza got back to winning ways in Paris by beating Russia's Svetlana Kuznetsova, another former Roland Garros champion.
Rafael Nadal of Spain reacts after winning against Simone Bolelli of Italy during their men's first round match during the French Open tennis tournament at Roland Garros in Paris, France, 29 May 2018.
The Russian, who was Paris champion in 2012 and 2014, fired 35 winners in her victory on Court Suzanne Lenglen.
Armed with an unseen physical strength, lethal forehand, picture-perfect anticipation and an iron determination, Nadal had conquered eight ATP titles on clay in 2005, including his maiden Grand Slam at Roland Garros that earned his place among the tennis immortals at such a young age.
"Can she do it?"
The 36-year-old downed Kristyna Pliskova of the Czech Republic 7-6 (4), 6-4 as she played in her first Major since the 2017 Australian Open where she triumphed.
"I'm ready for tomorrow, I feel strong in my legs", Halep, runner-up a year ago, said on court.
Third-seeded Marin Cilic also started his Paris campaign with a straight-set win over James Duckworth while up-and-coming Canadian teen Denis Shapovalov got past John Millman 7-5 6-4 6-2.
The former world number one will next face French wildcard Fiona Ferro, who stunned German Carina Witthoft - a player ranked nearly 200 places above her - 6-4 6-2.