Marco Cecchinato upset the odds to oust fifth seed Marcos Baghdatis in round one of the Nastase Tiriac Trophy, as Paul-Henri Mathieu also suffered defeat on Tuesday.
Baghdatis, a former Australian Open finalist, is ranked some 60 places above his Italian opponent, but was beaten 6-2 6-4 in just one hour and 15 minutes at the clay-court tournament in Bucharest.
The Cypriot allowed Cecchinato too many opportunities on his serve, and the world number 99 was happy to accept the chances - converting three of five break points.
Cecchinato's compatriot Paolo Lorenzi proved too good for Diego Schwartzman, the seventh seed winning through 6-3 6-4 against the Argentine.
The pair had met twice before and had one win apiece on the red surface, but it was Lorenzi that improved his record in Romania.
Eighth seed Mathieu joined Baghdatis in falling at the first hurdle as qualifier Radu Albot emerged victorious 7-6 (7-0) 2-6 6-1. The world number 91 surged into a 5-0 lead in the decider and had no problems closing things out against a player ranked 31 places above him.
Former world number seven Fernando Verdasco was made to work hard for his progress to the second round, the Spaniard recovering after losing the first set to Aldin Setkic to win 6-7 (5-7) 6-1 7-5 after two hours and 34 minutes.
In other matches, Lucas Pouille was a comfortable 6-3 6-4 winner over Dusan Lajovic, but Daniel Gimeno-Traver had to fight back from a set down to see off Adrian Mannarino 3-6 6-4 6-4.
Robin Haase overcame Andrea Arnaboldi 7-6 (7-4) 6-4 and Illya Marchenko got the better of Dudi Sela 6-4 4-6 6-4.