The third-seeded Hantuchova won her lone career title here last year, defeating Justine Henin in the fourth round and former world No. 1 Martina Hingis in the final to become the lowest seed in history to win a Tier I event.
"I felt a lot of pressure before the first match, so I was glad to get through it without any problems today," said Hantuchova, who received a first-round bye as a seeded player. "As soon as I stepped onto the court it reminded me so much of last year."
The 19-year-old Slovakian has not won another tournament, but reached her third straight Grand Slam quarterfinal at the Australian Open in January. She has advanced to at least the quarterfinals in all four WTA Tour tournaments she has played this year, including a semifinal showing last month at Antwerp.
Hantuchova next meets Slovenia's Katarina Srebotnik, who defeated Belgian Els Callens 6-4, 6-0.
Top seed Kim Clijsters of Belgium held off Fabiola Zuluaga, 6-3, 7-5. Clijsters, a finalist here in 2001, won the final four games of the match to record her second win in as many meetings with the Colombian.
No. 6 Jelena Dokic of Yugoslavia became the highest seed to lose after falling, 6-1, 5-7, 6-3, to world No. 87 Barbara Ritter of Germany.
"I did not play smart enough," Dokic said. "And also I should have played a tougher first set. That got me down a lot. Once you lose a set so easily it's hard to come back. If I played a tougher first set it would have made a difference."
Eighth seed Chanda Rubin eased past French qualifier Marion Bartoli, 6-4, 6-3, to notch her 15th victory in 21 matches at this event.
In other results among the top 16 seeds, No. 10 Magdalena Maleeva of Bulgaria outlasted Stephanie Cohen-Aloro of France, 6-3, 2-6, 7-6 (7-1); Zimbabwe's Cara Black handed No. 11 Anna Pistolesi of Israel her fourth straight defeat, 7-6 (7-3), 6-3; No. 15 Dechy thrashed Russia's Evgenia Koulikovskaya, 6-2, 6-1; and No. 16 Amanda Coetzer of South African routed Klara Koukalova of the Czech Republic, 6-2, 6-2.
Swim Week Miami Beach 2014 [PHOTOS]