Federer outlasts 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.
"I made sure I had a lot of first serves in, made sure I stayed aggressive from the baseline," Federer said. "I think it worked really well, hardly any unforced errors.
"I was able to move Ivo around and I was able to maintain that throughout the match, which was key. I could focus a bit on returning while then holding serve, which is important against Ivo."
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 Friday's 74-minute win.
Spanish fourth seed David Ferrer made a winning comeback after missing Indian Wells with injury, defeating Russia's Teimuraz Gabashvili, 6-4, 6-0
French ninth seed Richard Gasquet reached the third round by beating Alejandro Gonzalez of Colombia 7-6 (9/7), 6-4.
China's Li Na reached the third round in the women's tournament after Russia's Alisa Kleybanova withdrew from their tie with a viral illness.
The result sent the second seed into a contest against US teenager Madison Keys who put out Slovak 31st seed Daniela Hantuchova, 6-4, 6-2.
Two other seeds lost in upsets as American Varvara Lepchenko put out seventh seeded Jelena Jankovic 6-3, 2-6, 7-6 (7/2) and Czech Barbora Zahlavova Strycova beat Italian number 13 Roberta Vinci, 6-4, 2-6, 7-5.
Australian Open finalist and 10th seed Dominika Cibulkova defeated Yvonne Meusburger 6-1, 6-2.