Halle (Germany), June 15 : World No.2 Daniil Medvedev of Russia suffered a major blow to his Wimbledon preparations as world No. 45 Jan-Lennard Struff of Germany beat him 7-6(6), 6-3 in the opening round of Noventi Open, a grass-court tournament, on Tuesday. This was the 31-year-old Struff's biggest career victory. Struff will take on world No. 76, Marcos Giron of the USA, in the pre-quarterfinals. Giron got the better of Vasek Pospisil of Canada 7-6(4), 7-6(6). Making his eighth appearance in Halle, an ATP 500 tournament, Struff recovered from 2-5 down in the first set to score a hard-fought win against the top-seeded Russian, who had reached the French Open quarter-finals and lost to Stefanos Tsitsiipas. Halle debutant Lloyd Harris of South Africa broke serve once in each set to overcome eighth-seeded Frenchman Gael Monfils 6-4, 6-4. The South African, who reached the Dubai Duty Free Tennis Championships final in March this year, will challenge Slovakian qualifier Lukas Lacko in the pre-quarterfinals. Lacko beat Guido Pella of Argentina 6-7(5), 7-5, 6-1. Japan's Kei Nishikori, the 2014-15 semi-finalist, had to work hard to beat Ricardas Berankis of Lithuania 6-3, 2-6, 6-2 in one hour and 41 minutes. Nishikori now meets American Sebastian Korda, who defeated Spain's Roberto Bautista Agut 6-3, 7-6(0). An ecstatic Struff said after beating Medvedev that, "This is the biggest win of my career and to do it here on home soil is very special. I live only an hour from here." "Last time in Cincinnati (at the 2019 Western & Southern Open), Medvedev killed me 6-2, 6-1, it was really tough," added Struff. /IANS