Canadian fifth seed Milos Raonic was knocked out of the ATP Halle Open at the first-round stage on Tuesday, going down in straight sets to France's Gael Monfils.
Currently ranked 67th in the world, Monfils is unseeded in the grass-court season-opener but he reproduced the kind of form that once took him into the world's top 10 to win 6-4, 6-2 in just over an hour on court.
"I felt good and read his game well. When you are feeling good, you need to make the most of it," said Monfils, who beat world number six Tomas Berdych on his way to the third round of the French Open at Roland Garros.
Monfils broke Raonic three times altogether, including in the second game on his way to winning the opening set in just 26 minutes. A semi-finalist in Halle in 2011, Monfils will face Czech qualifier Jan Hernych next.
Raonic was not the only seed to fall on Tuesday, with Polish seventh seed Jerzy Janowicz suffering a shock defeat in three sets at the hands of Bosnian outsider Mirza Basic.
The 21-year-old Basic, ranked 240th in the world, is taking part in Halle as a lucky loser following the withdrawal of Philipp Petzschner due to a shoulder problem and his meeting with Janowicz was his first match on the ATP World Tour circuit.
Basic was broken twice but eventually prevailed in a deciding tie-break after just over two hours on court, winning 7-6 (7/5), 3-6, 7-6 (7/5).
"It was just my eighth match on grass," admitted Basic, who was only told he would be replacing Petzschner late on Tuesday morning.
Basic will face German wild card Mischa Zverev in the second round, with top seed and five-time champion Roger Federer likely to await the winner.
Elsewhere on Tuesday, Ernests Gulbis of Latvia beat former Australian Open finalist Marcos Baghdatis of Cyprus in three sets to set up a second-round meeting with third seed and defending champion Tommy Haas.