Haas defeated Ernests Gulbis 6-0, 3-6, 6-4. Gulbis managed four break chances in the second set -- finishing one -- but Haas won nearly 80 percent of the points while serving the first and third sets.
Gulbis dropped just six points on serve in the third set but Haas grouped enough together to post the only break of the set and advance.
He draws fifth-seeded Fabio Fognini in Friday's quarterfinals. Fognini was a 6-1, 6-3 winner over Leonardo Mayer. He ended up with six breaks on the day.
Fourth-seeded Benoit Paire stopped Nikolay Davydenko 6-3, 6-1 without dropping serve and Victor Hanescu beat Thomaz Bellucci 6-1, 6-4 to set up another quarterfinal. Neither Paire nor Hanescu dropped serve Thursday.