Kohlschreiber, Lopez, Monfils in quarterfinals

Philipp Kohlschreiber of Germany, Feliciano Lopez of Spain and Gael Monfils of France reached the quarterfinals of the BA Tennis Trophy on Thursday.

Kohlschreiber advanced when third-seeded Juan Martin del Potro of Argentina pulled out due to inflammation of a right toe. Kohlschreiber will meet fifth-seeded Fernando Verdasco of Spain on Friday.

Del Potro, who has won four ATP titles this season, broke a toe nail at last month's U.S. Open and the injury worsened during his first-round win over Martin Fischer of Austria on Wednesday.

He was unable to play despite medical treatment early Thursday, organizers said.

The eighth-seeded Monfils beat Radek Stepanek of the Czech Republic 6-4, 6-3 and will play second-seeded Fernando Gonzalez of Chile.

Monfils had two breaks to one in the first set. He broke twice more in the second after dominating with powerful forehand groundstrokes.

Lopez, who won the tournament in 2004, defeated Santiago Giraldo of Colombia 7-6 (5), 6-3.

Lopez will play either Juan Carlos Ferrero of Spain or Jurgen Melzer of Austria, who met later Thursday.