Forty-year-old Ivo Karlovic continued to defy the sands of time at the French Open.

By beating Feliciano Lopez 7-6 (4) 7-5 6-7 (7) 7-5 in the opening round at Roland Garros, the giant Croatian became the oldest man to win a grand slam singles match since Ken Rosewall at the Australian Open 41 years ago.

Lopez is no spring chicken himself at 37 and between them they made it the oldest match at the French Open in the Open era and the oldest at any slam since Rosewall played Ion Tiriac in Melbourne in 1977.

Karlovic will face Australian Jordan Thompson in round two.

Fifth seed Alexander Zverev found himself embroiled in another five-set battle at Roland Garros before recovering to beat John Millman 7-6 (4) 6-3 2-6 6-7 (5) 6-3.

Zverev had a series of long matches before running out of gas in the quarter-finals here last year, and it took him four hours and eight minutes to battle past Australian Millman in the longest match of the tournament so far.

"Today was a tough one," he said. "I'm excited for what's coming ahead. Most important, I'm still in the tournament, and that's all that matters."

Zverev won his first tournament of the season in Geneva on Saturday and bristled at the suggestion he has had a difficult year.

"Everybody keeps on saying I had a tough year," said the 22-year-old. "I mean, I'm still number five in the world. So it's not that bad. Somebody having a tough year is probably outside of the top 50."

Zverev's epic was followed by two lengthy women's matches on Court Philippe Chatrier, meaning local favourite Gael Monfils did not begin his opening-round contest against Japan's Taro Daniel until nearly 8pm.

The 14th seed is not known for quick matches but, with the deadline of the fading light, he was impressively focused in a 6-0 6-4 6-1 victory that finished at 9.34pm.

Eighth seed Juan Martin Del Potro had a tricky start against the dangerous Chilean Nicolas Jarry but finished strongly to win 3-6 6-2 6-1 6-4 while Monte Carlo champion Fabio Fognini was a 6-3 6-0 3-6 6-3 winner over fellow Italian Andreas Seppi