Rudolf Molleker

Molleker made his ATP main draw debut at the German Open in Hamburg after defeating, in the qualifying rounds, Casper Ruud and Leonardo Mayer, who later won the tournament as a lucky loser.

Molleker won his first ATP Challenger Tour title as a wildcard at the Heilbronner Neckarcup, defeating Jiří Veselý in the final. He won his first match at ATP-level at the Stuttgart Open, defeating compatriot Jan-Lennard Struff in the first round. At the 2018 German Open in Hamburg, as a wildcard, he beat former world No. 3 David Ferrer in the first round.

Molleker made his Grand Slam debut at the 2019 Australian Open, battling through three qualifying rounds before falling to world No. 16 Diego Schwartzman in four sets.

At the 2019 BMW Open he recorded his third ATP win over Marius Copil as a wildcard. He also entered the doubles event with Andre Begemann as an alternate pair. At the 2019 French Open, he performed a similar feat to the Australian Open, twice coming back from a set down to qualify for the main draw. He again lost in four sets in the first round, this time to Alexander Bublik. He received a wildcard in singles and in doubles for the main draw of the 2019 Hamburg European Open. He defeated two-time Hamburg champion Leonardo Mayer to record his fourth ATP singles win.

In 2021, he received a wildcard for the 2021 MercedesCup in Stuttgart, but lost to Marin Čilić. He received a wildcard in doubles at the 2021 Hamburg European Open partnering Daniel Altmaier. At the 2022 Hamburg European Open, having received a wildcard, he reached the second round of qualifying but lost to compatriot, 18-year-old and also a wildcard Marko Topo. He received a wildcard for the main draw at the 2023 Hamburg European Open but lost to compatriot and wildcard Maximilian Marterer. Ranked No. 179, he also received a wildcard for the main draw at the 2024 BMW Open, and defeated qualifier Francesco Passaro for his fifth ATP win.