DOHA, Qatar -- Tennis fans in the Gulf are used to seeing Serena and Venus Williams at the WTA Championships. Each sister won the season-ending title recently, and coming into this year's event, their images were everywhere from billboards to tournament programs.
Both were no-shows last week, though, because of injuries. And both will also miss this weekend's Fed Cup final in San Diego between the United States and Italy.
Sidelined by two operations on her right foot after getting cut by glass at a restaurant, Serena hasn't played a competitive match since winning Wimbledon on July 3. Hobbled by a bad left knee, Venus has only played in one tournament, the U.S. Open, since losing at the All England Club on June 29.
Serena turned 29 this year, Venus turned 30, and while neither has given any indication she is contemplating retirement, their extended absences have given everyone -- other players, fans, WTA officials and TV networks -- a chance to see what it is like to have a women's tennis tour without the two most famous and successful siblings their sport has ever seen.
"The absence of the Williams sisters at any event -- be it a major or non-major -- is significant," said Jason Bernstein, a senior director in ESPN's programming department. "Fans, print and electronic media interest, TV ratings and overall buzz are all reduced."
Serena has won 13 Grand Slam singles titles -- the most among active women, by far, and sixth in history -- and Venus has won seven. Despite their lack of playing time in 2010, both finished the WTA season in the top five. No other American woman is in the top 50, so Fed Cup captain Mary Joe Fernandez's roster instead includes No. 58 Bethanie Mattek-Sands, No. 67 Melanie Oudin and No. 115 Coco Vandeweghe.
Asked about not having the Williams sisters, Fernandez said: "Of course it's disappointing. The whole team was really looking forward to having both Venus and Serena on the team."
The interest generated by the Williams sisters' ascension -- both have been ranked No. 1, including Serena as recently as last month -- is widely credited with the decision to move the U.S. Open women's final to prime time in 2001. Venus beat Serena that year for the championship, and nearly 23 million viewers tuned in to the CBS broadcast, giving the final the largest TV audience of any program that night, including a football game between Notre Dame and Nebraska.
That 2001 U.S. Open final drew a 6.8 rating, and the Williams-Williams rematch the next year earned a 5.2. The only other U.S. Open women's final since 2001 with a rating higher than 2.7 came in 2008 -- the only other time a Williams reached the championship match in New York.
Bernstein called the sisters "game-changers for the sport" and "compelling to watch."
That said, Bernstein joined the WTA in insisting the tour is "well positioned" to withstand the eventual departures of the siblings -- just as it carried on after other major stars left, including Steffi Graf, Martina Navratilova and Monica Seles.
WTA chief executive Stacey Allaster called the Williamses "two of the most exciting and finest players we have had in our history" but said the tour can remain strong without them.
Allaster acknowledged it's likely that fewer Americans tuned into the WTA Championships this year because the Williams sisters did not play, but she said overall TV viewership around the globe was up 20 percent from 2009, perhaps because seven countries were represented in the eight-woman singles field.
"Every time there is changing of a generation of stars, one begins to ask these questions: Who will replace Andre? Who will replace Pete? Who will replace Martina, Monica, Steffi?" Allaster said. "It's very natural for all of us to say 'Who is next?' Who is the next generation of stars who is going to take the WTA to the next level?
"What we know definitively is that women's tennis has gone from strength to strength with each generation of stars," Allaster added. "I hope [the Williams sisters] stay around for many more years and hope they are healthy to do that. But I'm also incredibly confident in the product we have and the depth of athletes we have."
At the WTA Championships last week, the Williamses' absence was hard to miss.
"I just feel sorry for Williams sisters, that they are not here," said two-time major finalist Elena Dementieva, who announced her own retirement in Doha. "With them, it's really interesting and challenging for the rest of the players."
Some spectators felt jilted when they heard neither Williams would be at the tournament.
"I'm a bit disappointed. They are the two players everyone has heard of," said Gemma Swan, a British fan who was at the Doha tournament with her husband and baby daughter. "We were quite excited to see them. It's exciting when the two sisters are in the finals together."
These days, Caroline Wozniacki -- a 20-year-old Dane who replaced Serena at No. 1 -- is considered one of the tour's big draws, along with two-time major finalist Vera Zvonareva of Russia and 10th-ranked Victoria Azarenka of Belarus.
None of those three has won a Grand Slam title yet.
Like Allaster, current players sound convinced someone will emerge to take the tour forward.
"There will be new champions," said Kim Clijsters, the three-time U.S. Open champion who beat Wozniacki in the final at Doha last weekend. "That is the great thing about the sport. While we are sitting here talking, there are players practicing and living tennis out there who are going to be in the position that maybe Venus and Serena are in. We just don't know it yet."