Federer beats Karlovic in Miami opener
Roger Federer of Switzerland serves against Ivo Karlovic of Croatia during the Sony Open at Crandon Park Tennis Center on March 21, 2014 in Key Biscayne, Florida - by Clive Brunskill
The fifth-seeded Swiss, now 11-1 all-time against the Croatian, was impeccable in the opening set, losing his only point on serve as he stood 5-4, 40-0 moments before serving out the opener.
A winning tie-break in the second finally made the difference for Federer, now 42-12 in Miami with titles in 2005 and 2006.
Federer missed the tournament a year ago as he rested with back pain but has turned his 2014 season around after a low-key 2013.
Last weekend's finalist at Indian Wells withstood 13 aces from the big-hitting Croatian in the 74-minute win.
Spanish fourth seed David Ferrer made a winning comeback after missing Indian Wells with injury, defeating Teimuraz Gabashvili 6-4, 6-0
French ninth seed Richard Gasquet reached the third round over Alejandro Gonzalez of Colombia 7-6 (9/7), 6-4.
China's Li Na reached the third round on the women's side as intended opponent Alisa Kleybanova withdrew with viral illness before their match.
The result sends the second seed into a contest against the winner from Daniele Hantuchova and American Madison Keys.
Two seeds lost in upsets as American Varvara Lepchenko put out seventh seeded Jelena Jankovic 6-3, 2-6, 7-6 (7/2).
Czech Barbora Zahlavova Strycova beat number 13 Italian Roberta Vinci Italy, 6-4, 2-6, 7-5 while Australian open finalist and 10th seed Dominika Cibulkova defeated Yvonne Meusburger 6-1, 6-2.