Roger Federer squandered a match point as he was shocked by German veteran Tommy Haas in the second round of the Mercedes Cup in Stuttgart.
The 39-year-old Haas, who is playing his final season on the tour after a series of injury problems, battled to a 2-6 7-6 (8/6) 6-4 win in just under two hours.
Federer was playing his first tournament since he won the Miami Open in April after choosing to skip the clay court season to prepare for his favoured grass.
The Swiss star cruised through the first set in just 23 minutes and broke early in the second, but Haas deployed all of his considerable experience to fight back.
Federer hit a backhand long on a Haas second serve when he held match point in the tie-break, and the German punished him by converting his fourth set point.
Haas stepped up in the final set, saving three early break points before breaking for 3-1 and maintaining his advantage to clinch a memorable victory.