France's Gael Monfils and Gilles Simon suffered early exits from the Cincinnati Masters on Tuesday.
American James Blake, a former world number four, crashed out of the tournament in just 45 minutes but his compatriot Mardy Fish battled into the second round.
Fish produced a spirited display to defeat Simon 7-6, 7-5 and set up a match with Spanish eighth-seed Fernando Verdasco.
Monfils, the 16th seed, fell to Colombian qualifier Alejandro Falla 6-3, 6-4 while Blake's slide down the rankings continued with a 6-3, 6-0 loss to Uzbekistan's Denis Istomin.
The good news for France came with Richard Gasquet defeating 12th seeded Russian Mikhail Youzhny 2-6, 6-4, 6-1.
Czech seventh seed Tomas Berdych, the Wimbledon runner-up, began his campaign against Frenchman Paul-Henri Mathieu in straightforward fashion with a 6-4, 6-4 win in his second round match.
The top seeds, including world number one Rafael Nadal, begin their second-round matches on Wednesday.
Nadal will face American Taylor Dent while Roger Federer takes on Istomin and Britain's Andy Murray faces Frenchman Jeremy Chardy.
Roddick, Dent advance at Cincinnati Masters
Simon cruises past lethargic Roddick
Somdev fails to qualify for Toronto Masters
All smiles for Blake after crushing win at LA Open
Hewitt slays Dent