Anderson through to last eight
Kevin Anderson, bidding for his second Delray Beach Open crown in three seasons, reached the quarter-finals on Wednesday when Ivo Karlovic retired with a stomach virus.
The South African fourth seed held serve in the opening game and was poised to break when the big-serving Croatian called it quits.
Karlovic was coming off a run to last Sunday's ATP final at Memphis, where he lost to Japanese top seed Kei Nishikori.
Anderson could next face Australian Marinko Matosevic, who he beat in the 2012 final, for a place in the semi-finals, but only if he can overcome fellow countryman Lleyton Hewitt.
Spanish sixth seed Feliciano Lopez rallied to eliminate Frenchman Adrian Mannarino 4-6 6-4 6-2 and will next face either US qualifier Steve Johnson or German top seed Tommy Haas.
Croatian seventh seed Marin Cilic reached the second-round after beating Germany's Benjamin Becker 6-1 6-3.
Cilic, a champion at Zagreb and runner-up at Rotterdam last week, will next meet home favourite Ryan Harrison.