Alexander Zverev eventually controlled his nerves to reach the French Open third round with a 2-6 7-5 4-6 6-1 6-2 win over Serbian Dusan Lajovic.
Bidding to improve on a below-par grand slam record, the second-seeded German smashed a racquet in frustration before finding his groove and setting up a meeting with Bosnian Damir Dzumhur.
Zverev has yet to reach the last eight at a slam but his huge talent told in the end against the world No.60.
Asked about the gap between his ATP tour and his grand slam performances, Zverev said: "Everybody tries to make a bigger story out of it than it is.
"I have had great success on the ATP Tour, won three Masters, made two other finals this year.
"I'm not worried. I know if I'm doing the right things and if I do the right work I'll win those long matches, and the success will come itself. This is not something I think of on a daily basis."
After all, 20-times grand slam champion Roger Federer was also a relatively late bloomer.
"He (Federer) told me a story about how he never made it past quarters until he was, what, 23 years old or something like that," said Zverev.
"I still have a little bit of time. Hearing that from the greatest player of all time is comforting because you always think, 'Oh, if I'm not going to win this one, I'm never going to win one.'"
Federer was in fact just shy of 22 when he won Wimbledon for his first slam.
Either way, the 21-year-old Zverev had to cope with the frustration of an error-riddled start against Lajovic.
He dropped serve twice in the opening set as Lajovic kept his cool and held serve to take the lead.
Lajovic toyed with the German, who lost his temper when he was broken in the third game of the second set and crushed his racquetet in frustration.
Horrible unforced errors and ill-timed rushes to the net followed as Zverev struggled for control but he broke back for 3-3 and regained his composure to convert his first set point on Lajovic's serve to level the match.
There were more jitters, though, as he trailed 2-1 in the third when he dropped serve on a double fault. Lajovic went on to bag the set and Zverev had his back to the wall.
But the German, who leads the ATP Race, was fully focused as he raced through the fourth set by sticking closer to the baseline and he ended the match with an unreturnable serve.