Alexander Zverev on Thursday became the first 17-year-old to reach the quarter-finals of an ATP 500-level tournament since Rafael Nadal in 2004 when he made the Hamburg last-eight.
The former top junior from Germany, who is ranked 285 in the world, defeated experienced 11th seed Santiago Giraldo 6-4, 7-6 (8/6) having already beaten Russian fifth seed Mikhail Youzhny in the previous round.
"He's a tough player and a really tough competitor," said Zverev. "He got the break when I was serving at 5-4 and I just had to focus and play my game. Luckily, I got through in two sets."
Nadal was the last 17-year-old to make the last eight of an ATP 500 tournament at Dubai in 2004.
On Friday, Zverev will meet compatriot Tobias Kamke where he will bid to become the first 17-year-old player to reach the semi-finals or better at a tour-level event since Marin Cilic at Gstaad in 2006.