'Can't do that': Tennis fans in disbelief at Daniil Medvedev meltdown

Daniil Medvedev's preparations for Wimbledon have started in brutal fashion after the World No.2 blew a big lead in a shock first-round exit from the ATP 500 tournament in Halle.

Medvedev was beaten 7-6 (7-3) 6-3 by Germany's Jan-Lennard Struff on Tuesday in his first match of the grass-court season.

SAY WHAT: Novak Djokovic's shock move ahead of Wimbledon

'APPALLING': Tennis fans rage over Wimbledon announcement

The Russian star opened up a commanding 5-2 lead in the opening set, but let Struff roar back into the contest after blowing a set point.

The 45th-ranked Struff then managed to force a tie-breaker that he went on to win.

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.

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 last week, could be seen angrily smashing his racquet after netting a forehand on match point.

He will hope to rediscover his touch on grass before he resumes his pursuit of a maiden grand slam title at the All England Club starting June 28.

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

Fans were left in disbelief over Medvedev's ignominious start to the grass-court season.

Alexander Zverev overcomes scare to advance

Meanwhile, sixth-ranked Alexander Zverev overcame a mid-match blip to defeat fellow German Dominik Koepfer 6-4 3-6 6-3.

The French Open semi-finalist will play Ugo Humbert next, who defeated Sam Querrey 4-6 7-6 (7-4) 7-6 (7-5).

Andrey Rublev didn't face a single break point as he won an all-Russian match with Karen Khachanov 6-3 7-6 (7-5) to set up a second-round meeting with Australian Jordan Thompson.

Felix Auger-Aliassime earned a second-round match against 10-time Halle champion Roger Federer with his 6-3 7-5 win over of Hubert Hurkacz.

Lloyd Harris managed another upset win as the South African beat eighth-seeded Gael Monfils 6-4 6-4, while Kei Nishikori won his opening-round match 6-3 2-6 6-2 over Ricardas Berankis.

On Monday, Stefanos Tsitsipas pulled out of the Wimbledon warm-up event because of personal reasons after the death of his grandmother before the French Open final.

The 22-year-old revealed in an emotional social media post that he had learned of the death of his paternal grandmother just five minutes before taking the court.

"Five minutes before entering the court my very beloved grandmother lost her battle for life," Tsitsipas wrote on Instagram.

"A wise woman whose faith in life, and willingness to give and provide can't be compared to any other human being that I have ever met.

"It's important to have more people like her in this world. Because people like her make you come alive. They make you dream."

with AAP

Watch 'Mind Games', the new series from Yahoo Sport Australia exploring the often brutal mental toil elite athletes go through in pursuit of greatness:

Click here to sign up to our newsletter for all the latest and breaking stories from Australia and around the world.