The surprise early elimination of the top four seeds made the Williams sisters' progress to the Wimbledon final harder not easier, Serena said on Thursday.
Serena Williams reached a third final at the All England Club against sister Venus when she beat Chinese wildcard Zheng Jie while title holder Venus also won her semi-final against Russian fifth seed Elena Dementieva.
"It might even have made it tougher when the top players go out," twice champion Serena, at number six seeded one place higher than Venus, told reporters.
She said the fact that top seeds Ana Ivanovic, Jelena Jankovic, Maria Sharapova and Svetlana Kuznetsova had lost before the quarter-finals could have given lower ranked players the belief they could upset other elite players.
Sharapova, who beat Serena in her last Wimbledon final in 2004, was upset in the second round, French Open champion Ivanovic in the third and Jankovic and fourth seed Kuznetsova in the fourth.
The Williams sisters contested the 2002 and 2003 finals with Serena winning both, although Venus has a total of four Wimbledon titles.
Serena said it was not at all difficult to motivate herself to beat Venus whenever they meet. They have contested nine matches at grand slam tournaments including six finals, five of them won by Serena.
"It's easy, especially with sibling rivalry... I want everything she has," Serena, at 26 two years younger than Venus, said.
Asked whether it mattered to her to try and chalk up more Wimbledon wins than Venus, Serena said with a grin: "We just count the grand slam total, that's what counts."
Serena has eight grand slam titles to Venus's six, winning her last at the Australian Open in January 2007 when she was ranked only 81 after injury marred her 2006 season.
The younger Williams feels she is now back in top form, saying of her performance on Thursday: "I was especially excited
with my game, I was better serving, better moving.
"I'm definitely going to have to serve well (in the final)."
Serena would not discuss the weak points she might see in her sister that she could exploit on Saturday and was only thinking as far ahead as Friday's doubles semi-final which the sisters will play against Nathalie Dechy of France and Casey Dellacqua of Australia.
"We're both so elated to be here, tomorrow we have the doubles, that's the only thing on the schedule right now."