World number three Alexander Zverev was forced to quit his French Open preparation early after a surprise last-16 defeat to Frenchman Alexandre Muller at the Hamburg Open on Wednesday.
Muller, ranked 40th globally, triumphed 6-3, 4-6, 7-6 7/5, marking his first win over a top-five opponent.
Zverev struggled through the first set, taking just two games as Muller dominated in 34 minutes. The German bounced back in the second set, breaking Muller twice to level the match.
The final set was tightly contested, with both players exchanging breaks before heading into a tiebreak. Despite leading early, Zverev lost the final three points to Muller.
A late addition to the tournament, Zverev had hoped to build momentum in his hometown event ahead of the French Open.