ATP roundup: Richard Gasquet wins in Metz after saving match point
Gasquet, 38, announced he will retire after the French Open next summer. Back in 2004 Metz was the site of his first of 33 ATP Tour finals appearances.
The former World number seven had 14 aces and won 49 of 55 first-serve points (89.1 per cent) against Monteiro; he saved match point to tie the third-set tiebreaker 6-6 and won the next two points to finish the job.
French lucky loser Pierre-Hugues Herbert upset sixth-seeded Pedro Martinez of Spain 6-3, 3-6, 7-6 in two hours and 32 minutes. Herbert finished with a 12-4 edge in aces.
Seventh-seeded Jan-Lennard Struff of Germany charged past Kazakhstan's Alexander Shevchenko 3-6, 6-4, 6-4. Great Britain's Cameron Norrie, French qualifier Quentin Halys and Italian Lorenzo Sonego also advanced out of the first round.
Belgrade Open
Seventh-seeded Tomas Martin Etcheverry of Argentina saved all four break points he faced and defeated Russia's Pavel Kotov 6-3, 6-4 in first-round action in the Serbian capital.
Etcheverry's next opponent will be Slovakian qualifier Lukas Klein, a 6-4, 6-2 winner over Australia's James Duckworth.
German Daniel Altmaier upset Italian eighth seed Luciano Darderi 7-6, 6-3, and Dusan Lajovic pleased the home crowd by knocking out ninth seed Mariano Navone of Argentina 6-0, 7-6.
Other winners were Canadian qualifier Denis Shapovalov, Croatia's Marin Cilic, Australian Christopher O'Connell and American Aleksandar Kovacevic.