Stepanek, seeded No. 5, emerged the winner of a 7-6 (7-4), 5-7, 7-6 (7-5) match with Lacko that saw 250 points over 2 hours, 42 minutes. Stepanek had a break in each set but needed to win the third-set tiebreaker to get past Lacko.
Eighth-seeded Lukas Rosol, like Stepanek from the Czech Republic, also qualified for the quarterfinals, topping Mirza Basic 6-3, 7-5. Rosol won nearly 70 percent of the points on serve and saved three of the four break points he faced. He was able to finish off three breaks himself, including one that decided the second set.
The first round wrapped up with a pair of matches. Lukasz Kubot had 10 aces en route to a 7-6 (7-1), 6-4 decision over Florian Mayer and Jaroslav Pospisil edged sixth-seeded Gael Monfils 7-6 (7-0), 7-5.
It was the first main-draw win of the year for Pospisil, who could meet his brother Vasek, the tournament's No. 7 seed, in the semifinals.