Alexander Zverev, aged 18, had never faced a player younger than himself on the ATP World Tour coming into this week. But on Monday at the If Stockholm Open, the German was given all he could handle by 17-year-old Mikael Ymer before winning 7-6(9), 6-7(5), 6-4. The Swedish wild card, ranked No. 617, kept pace with the World No. 83 for two and a half hours before succumbing.

“Ymer played unbelievably from the beginning, and I wasn’t expecting that,” said Zverev, who capitalised on the lone break point of the deciding set to earn the win “He just needs to keep working hard and he’ll be someone to look out for in the future. I don’t think he was nervous at all today. In the second set, I was in control but he fought back well. It was an interesting match in the end.”

In the second round, Zverev will take on top seed Tomas Berdych.

Elsewhere, ATP Comeback Player Of The Year candidate John Millman maintained his form by taking out Benjamin Becker 7-6(2), 6-3. Millman, ranked 76^th in the Emirates ATP Rankings, saved four of five break points in the 95-minute win.