Roger Federer suffered a shock 3-6 7-6(7) 7-6(5) loss to world number 116 Evgeny Donskoy of Russia in the Dubai Open second round on Wednesday.
Swiss Federer, playing his first tournament since winning his 18th grand slam title at the Australian Open in January, wasted three match points in the second set and led 5-2 in the third before the 26-year-old Donskoy fought back.
Third seed Federer, the former world number one and seven-times champion in Dubai, surged 5-1 ahead in the deciding tiebreaker but qualifier Donskoy reeled off six points in a row to secure a remarkable victory.
Earlier, top seed Andy Murray beat Guillermo Garcia-Lopez 6-2 6-0 to reach the last 16.