World number two Daniil Medvedev was a first-round casualty at the ATP grass court tournament in Halle on Tuesday as he suffered a shock defeat to Germany's Jan-Lennard Struff. Struff, ranked 45th in the world, bounced back from 5-2 down in the first set to claim a 7-6(8/6), 6-3 victory over the Russian, who was the top seed in Halle. "This is the biggest win, rankings wise, of my career and to do it here on home soil is very special. I only live an hour from here," said Struff, 32, after his first career win over Medvedev at the fourth attempt. Having stunned Medvedev, this year's Australian Open finalist, Struff will now play American qualifier Marcos Giron in the second round. The German said his run to the last 16 of Roland Garros, where he lost to Diego Schwartzman over three sets, boosted his confidence. Struff is now hoping for another good run on home soil having reached the final of the Munich tournament on clay in May. Swiss tennis ace Roger Federer, who turns 40 in August, will play 20-year-old Felix Auger-Aliassime in the second round after the Canadian's 6-3, 7-5 first-round win over Hubert Hurkacz of Poland. Fourth seed Andrey Rublev played his first game on grass for two years as he beat his doubles partner Karen Khachanov 6-3, 7-6(7/5) in the first round. Earlier, South Africa's Lloyd Harris will face Slovakian qualifier Lukas Lacko in the second round after knocking out eighth-seeded Frenchman Gael Monfils for a 6-4, 6-4 win. Japan's Kei Nishikori will play Sebastian Korda of the USA in the next round after his hard-fought 6-3, 2-6, 6-2 win over Ricardas Berankis of Lithuania. ryj/dmc