Russia's Daniil Medvedev serves the ball to Reilly Opelka of the US during their men's singles third round tennis match on Day 6 of The Roland Garros 2021 French Open tennis tournament in Paris on June 4, 2021. (ANNE-CHRISTINE POUJOULAT / AFP)

World number two Daniil Medvedev's Wimbledon preparations suffered a setback on Tuesday when he was bundled out by Germany's Jan-Lennard Struff 7-6(3) 6-3 in the opening round of the ATP 500 tournament in Halle.

In his first match of the grasscrout season, top seed Medvedev made a bright start to open up a commanding 5-2 lead in the opening set before Struff roared back into the contest.

World number 45 Struff saved a set point to draw level and force a tiebreak where he grabbed an early lead to take the opening set.

The match was one-way traffic in the second set as Struff broke his Russian opponent twice to secure the biggest victory of his career.

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Struff has now won 10 of his last 15 matches, which includes an impressive run to a maiden ATP Tour final in Munich followed by his first Grand Slam last-16 appearance at the French Open last week.

Medvedev, who suffered a quarter-final exit at the French Open, will hope he rediscovers his touch on grass before he resumes his pursuit of a maiden Grand Slam title at Wimbledon starting June 28.

He has never progressed beyond the third round at the grasscourt major since his main draw debut in 2017.