World number one Lindsay Davenport [ Images ] began her quest for a record fifth Pan Pacific Open title with a comfortable 6-4, 6-3 win over Japan's [ Images ] Saori Obata on Thursday.

Russia's [ Images ] Elena Dementieva [ Images ] crushed Japan's Akiko Morigami 6-2, 6-2 to join Davenport in Friday's quarter-finals.

Defending champion Davenport, beaten by Serena Williams [ Images ] in the Australian Open [ Images ] final last weekend, dropped her first two service games in Tokyo.

The American uncharacteristically threw down her racket in disgust after squandering five set points at 5-3 in the first set.

But she quickly recovered and went on to clinch victory with a pummelling cross-court backhand to reach the last eight of the $1.3 million event she won in 1998, 2001, 2003 and 2004.

"To be honest, I still felt a little worn down," said Davenport, who suffered a final set collapse in Melbourne [ Images ] in her 2-6, 6-3, 6-0 defeat by Williams.

"A Grand Slam final is the toughest loss to get over. I probably had the biggest lapse of my career and it's going to take a few weeks to get it out of my system."

Davenport next plays Czech Iveta Benesova [ Images ], who battled past Japan's Aiko Nakamura 3-6, 7-5, 6-4.

Fourth seed Dementieva had few problems against Morigami and will next face another Japanese player, Shinobu Asagoe, who overwhelmed Italy's [ Images ] Roberta Vinci 6-0, 6-2.

Dementieva lost two Grand Slam finals last year Anastasia Myskina [ Images ] in French Open [ Images ] and Svetlana Kuznetsova [ Images ] at the U.S. Open, but believes she could go one better this season.

"I feel much stronger now and I know what it takes to reach a Grand Slam final," said Dementieva. "I just feel I need to take one more step and I think I can do that this year."

Sixth seed Elena Likhovtseva battled past American Jill Craybas 7-5, 4-6, 6-2 to set up an all-Russian quarter-final with Wimbledon [ Images ] champion Maria Sharapova [ Images ].

Slovakian eighth seed Daniela Hantuchova [ Images ] beat Russia's Maria Kirilenko 4-6, 6-0, 6-2 and will play U.S. Open champion Kuznetsova in the last eight.

(Additional reporting by Ben Rimron)