American Andy Roddick, Mardy Fish, James Blake, and Sam Querrey reach the San Jose quarter-final .
Top seed Roddick will face German Tommy Haas, after conquering Ernest Gulbis 6-3, 7-6 (3) .
Compatriot Mardy Fish advanced to quarter-final to compete against Juan Martin del Potro, who gain 6-2, 6-2 win over Japanese Kei Nishikori . Meanwhile, Fish beat another American, John Isner, in uneasy three sets, 6-2, 6-7 (4) 7-5.
James Blake book a quarter-final clash with six-seeded local player Sam Querrey. Blake downs Florent Serra of France 6-3, 6-4 while Querrey vanquished Denis Gremelmayr of Germany 6-3, 6-2.