Roger Federer will face a tricky opening tie at the Sony Open Tennis in Miami, with big-hitting Croatian Ivo Karlovic awaiting the Swiss in the second round.
The fifth seed received a bye into the next round and Karlovic ensured he will join Federer on court by beating French qualifier Paul-Henri Mathieu 7-6 (7/3) 7-6 (7/5) in his opening match.
Jeremy Chardy also battled through to the second round with a 7-5 3-6 7-6 (7/5) victory over Juan Monaco of Argentina. Chardy's reward for his progress is a match-up with second seed Novak Djokovic, who won in Indian Wells last weekend.
Teymuraz Gabashvili will also face one of the top seeds in his next match. A meeting with David Ferrer is on the cards after the Russian won his opening-round clash against Marcel Granollers 6-4 6-3.
Matthew Ebden of Australia was a 4-6 6-4 6-4 victor over Poland's Lukasz Kubot, setting up a second-round match-up with sixth seed and Wimbledon champion Andy Murray.
Former world number three Nikolay Davydenko saw his challenge ended at the first hurdle with a straight-sets defeat to Adrian Mannarino, but Radek Stepanek impressed in a 6-3 6-0 rout of German Daniel Brands.
Former Australian Open finalist Marcos Baghdatis came through a real fight to beat Santiago Giraldo 1-6 6-2 7-5 but Lukas Rosol was eliminated as world number 86 Dominic Thiem built on his run through qualifying with a notable 7-6 (8/6) 6-4 win.
Julien Benneteau came from a set and a break down to see off British teenager Kyle Edmund 6-7 (2/7) 6-3 6-2, while other first-round winners included Albert Montanes of Spain, Croatian Ivan Dodig and Dutchman Thiemo De Bakker.
In the women's event, a host of American players gave the home crowd reason to cheer by progressing to the second round.
Vania King demolished Estrella Cabeza Candela 6-0 6-0, Lauren Davis ousted China's Shuai Zhang 6-2 6-3 and Coco Vandeweghe beat Marina Erakovic 6-4 7-6 (8/6).
Christina McHale overcame Jie Zheng 6-4 6-2, Alison Riske came from a set down to beat Nadiya Kichenok 1-6 7-5 6-2 and Madison Keys cruised past Estonian wild card Anett Kontaveit 6-3 6-2 in the final match of the night.
Youth got the better of experience when 17-year-old Croatian Donna Vekic ended the challenge of 43-year-old Kimiko Date-Krumm 7-6 (7-2) 6-2, while Nadia Petrova made the most of a wild card by beating Urszula Radwanska 7-5 1-6 6-4 and Germany's Andrea Petkovic was a 6-3 6-4 winner against Spaniard Maria-Teresa Torro-Flor.
French qualifier Virginie Razzano advanced another step in the tournament with a 6-4 6-0 victory over Britain's Heather Watson, with Holland's Kiki Bertens, China's Shuai Peng and Patricia Mayr-Achleitner of Austria among the other first-round winners.