MADRID. Serena Williams and Maria Sharapova reached the quarterfinals at the Madrid Open on Thursday, with the two top-ranked players winning in straight sets. Williams needed a little more than an hour to defeat Maria Kirilenko 6-3, 6-1, after Sharapova got past Sabine Lisicki of Germany 6-2, 7-5.Top-ranked Williams dominated Kirilenko, who dropped the first set with one of several unforced errors. The defending champion also used a strong serve and return game, working the 12th-ranked Russian back and forth on the baseline of the red clay court with her precise forehand drives.‘’I just felt really relaxed, like I was taking my time,’’ Williams said. ‘’I had been missing my serve when I was hitting it harder, so I took some pace off and didn’t hit as hard as I usually do.