Simon beat Canadian qualifier Frank Dancevic 6-1, 6-2 and Monfils eliminated Marat Safin of Russia 6-2, 3-6, 6-2.
The 14th seed, Marin Cilic of Croatia, was upset by Russian Mikhail Youzhny 4-6, 7-6 (7-4), 6-1.
Other first-round winners Monday included Leonardo Mayer of Argentina, Stanislas Wawrinka of Switzerland, Philipp Petzschner and Rainer Schuettler of Germany and Jeremy Chardy and Paul-Henri Mathieu of France.
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