Auckland - Fourth-seeded Sam Querrey showed impressive form to advance to the Heineken Tennis Open quarter-finals on Wednesday, beating Belgian wildcard Olivier Rochus 7-5, 6-3 in just over an hour.
Querrey sent down 19 aces in an outstanding serving performance he described as one of the best of his career.
"That's probably one of the best serving matches I've ever played and everything felt pretty good," the American said. "It's my first match of the year, everything felt pretty good and I'm just looking forward to playing on Thursday."
Second-seed Philipp Kohlschreiber of Germany, who counts the 2008 Auckland tournament among his four career titles, had to work harder for his 7-6 (4), 4-6, 6-3 win over Colombia's Alejandro Falla.
Seventh-seeded Tommy Haas beat Igor Sijsling of the Netherlands 6-3, 6-4 in just over an hour to reach a quarterfinals matchup with Gael Monfils of France, who beat Australian qualifier Greg Jones, 6-4, 6-2 in 66 minutes.
Top-seeded David Ferrer was due on court later Wednesday. Ferrer is attempting to become the first player since the great Australian Roy Emerson to win the tournament four times, including three years in succession.
Monfils made an impressive statement of fitness and form as he claimed his place in the final eight. The Frenchman's ranking slumped from 13 in February, 2012 to 99 in January as he battled injuries and other setbacks through the year.