Federico Delbonis continued his momentum having sunk Roger Federer in Germany last week by ending Thomaz Bellucci's defence of the Swiss Open title.
The Argentine, who defeated the Swiss ace in the Hamburg semi-finals before going on to lose narrowly in the final, came through 7-5 7-6 (2) against Bellucci, a Brazilian, who also took the clay-court title at Swiss ski resort Gstaad in 2009.
The first set was very tightly contested. However, there were early signs that Bellucci would be the first to buckle under the pressure.
The 25-year-old had to save two break points in the sixth game before facing one more break point in the twelfth game, which he conceded.
The second was decided by a tie-breaker which Bellucci started well but then suffered two mini-breaks on the sixth and seventh points, which ultimately determined his fate.
Delbonis will continue rising in the rankings after victory over Federer helped him climb from No 114 to 65 in the world.
Meanwhile, in the day's other matches, four Spaniards made it through to the next round as eighth-seeded Roberto Bautista Agut eased past Henri Laaksonen of Switzerland 6-2 6-3 while Daniel Gimeno-Traver beat Kenny De Schepper of France 6-4 6-4.
Guillermo Garcia-Lopez beat Adrian Ungur of Romania 6-4 6-7 (2) 6-1 and Pablo Andujar eliminated another Romanian, Victor Crivoi 6-1 6-2.
Elsewehere there were wins for Victor Hanescu and Robin Haase.