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The only former champions in the draw at the clay-court event, Zverev and Rublev each notched straight-sets wins to kick-start their 2025 campaigns. Competing in his hometown, top seed Zverev held firm after letting slip a 4-1 lead in the second set to secure a 6-1, 7-6(5) victory against qualifier Aleksandar Kovacevic.

“It was good. Especially the first set and a half was almost perfect,” said Zverev, who tallied 24 winners to just 12 unforced errors against the American. “Obviously I’m extremely happy about the level and looking forward to the next matches.

“[In the second set] he started hitting the ball extremely hard and being unbelievably aggressive, and sometimes I was not in control of the rallies anymore. Credit to him, and I’m happy with the win.”

The 28 year-old German has now won 13 of his past 15 matches in Hamburg, where he lifted the trophy in 2023 and reached the championship match a year ago. Awaiting the No. 3 in the ATP Rankings in the second round will be Alexandre Muller, who saw off Elias Ymer 6-3, 7-5. 

Earlier, 2020 titleist Rublev eased past Damir Dzumhur 6-4, 6-3 after winning 83 per cent (29/35) of points behind his first serve. 

The 27 year-old is aiming to build confidence in Hamburg this week after struggling so far this year on the European clay: Rublev has gone 3-8 since claiming his 17th ATP Tour crown in February in Doha.

Rublev, seeded to face Zverev in the semi-finals, will next face home hope, 17 year-old Justin Engel, who ousted Jan-Lennard Struff 7-6(4), 7-6(4). 

Engel joined elite company by becoming the third-youngest German to win a match in Hamburg in the Open Era, only behind Boris Becker and Zverev.

In other Monday action in Germany, Roberto Bautista Agut and Brandon Nakashima also advanced to the second round. Bautista Agut overcame Marcos Giron 7-6(5), 6-0.

While Nakashima led Raphael Collignon 6-5 when the Belgian qualifier retired due to a right thumb injury he sustained after he slipped on the baseline. 

Jiri Lehecka overcame Borna Gojo 6-4, 3-6, 6-2.