Fifth seed Alexander Zverev came through a frustrating first-round match against world number 56 John Millman in the French Open in Paris.

German Zverev, 22, smashed his racquet several times in a 7-6 (7-4) 6-3 2-6 6-7 (5-7) 6-3 win in over four hours.

He broke Australian Millman late in the deciding set to set up a second-round tie with Swedish qualifier Mikael Ymer.

Argentine eighth seed Juan Martin del Potro came through a scare to beat Chile’s Nicolas Jarry 3-6 6-2 6-1 6-4.

Del Potro, 30, won in just over two hours against the world number 58 on Court Suzanne Lenglen.

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Zverev, who reached the quarter-finals in Paris last year, has struggled for form since stunning world number one Novak Djokovic to win the ATP Finals in November.

“Everybody keeps on saying I had a tough year. I mean, I’m still number five in the world,” he said.

“So it’s not that bad. Somebody who is having a tough year is probably outside of the top 50 or something like that. I’m still top 10 of the race. That’s what matters.”

Zverev lost to Canadian world number 18 Milos Raonic in the fourth round of the Australian Open in January, during which he smashed a racquet during a changeover.

There were several roars of frustration during an underwhelming performance on Philippe Chatrier on Tuesday.

He opened up a two-set lead but was broken twice in the third and was dominated in a fourth-set tie-break. He also had a break point saved at 3-2 up in the fifth before completing victory.

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Del Potro survives scare

Del Potro, seeking a first Grand Slam since becoming US Open champion 10 years ago, will face Japan’s Yoshihito Nishioka in the second round.

A French Open semi-finalist last year, Del Potro dominated after falling a set behind as he broke Jarry’s serve five times.

Croatia’s 40-year-old Ivo Karlovic became the first man in his forties to compete in a Grand Slam singles match for 27 years as he beat Spaniard Feliciano Lopez 7-6 (7-4) 7-5 6-7 (9-7) 7-5.

With the combined age of 77 years, it was the oldest men’s match in history at Roland Garros.

The last player to contest a Grand Slam singles match aged 40 or older was American Jimmy Connors at the US Open in 1992.

Karlovic plays 25-year-old Australian Jordan Thompson in the second round.

Seventh seed Fabio Fognini beat fellow Italian Andreas Seppi 6-3 6-3 3-6 6-3 to reach the second round, where he will play Argentina’s Federico Delbonis.

Frenchman Gael Monfils, the 14th seed, saw off Japan’s Taro Daniel 6-0 6-4 6-1 to set up a meeting with Adrian Mannarino.