NEW YORK -- It's hard to imagine two celebrities with the candlepower of Venus and Serena Williams going out and about in this city without being pursued by a panting mob. Yet according to Venus, sometimes people keep their distance when the sisters are out shopping or running other errands.
And sometimes they don't.
"I'm walking the dog, and, like the other day, the bus driver jumped out of the bus," Venus said Sunday. "Stopped the bus, jumped out and was running."
Is it too soon to picture crowds as jazzed as that driver streaming into Arthur Ashe Stadium to see the sisters on a very different kind of excursion? Venus and Serena are on a collision course in the upper half of the U.S. Open draw, although their potential semifinal date definitely is entered in pencil, not indelible ink.
"That would be awesome because it would mean that there is a Williams in the final, and it would mean that Americans have a chance to win," Venus said circumspectly Sunday, unwilling to put any more emotional helium in the balloon just yet.
That's probably wise. Venus should face a substantial test in third seed Jelena Jankovic of Serbia. Serena would have to hurdle No. 1 Justine Henin, who lost to her on hard court in the Miami final, then beat her in the quarterfinals of the French Open and Wimbledon and is the one player besides Venus with an unwavering belief that she can beat anyone on any given day.
"We know each other pretty well," the Belgian star said Sunday after breezing to a 6-0, 6-2 win over Russia's Dinara Safina. "I know everyone was waiting for that match, and here we are. That's why I'm playing tennis, to play this kind of match.
"It was important for me to beat her on another surface than clay in Wimbledon. But it was very emotional for me. That took a lot of energy, that match. And I know it's going to be different, different surface. She's here at home. She loves to play in the U.S. Open."
If the Williamses manage to overcome their considerable quarterfinal opposition, they'll play each other for the first time in two years. It would be a key scene in Act IV of their remarkable careers, which have passed through Rise, Domination and Hiatus into Renaissance.
Serena looked stronger in the first three months of the season, winning the Australian Open and the prestigious Sony Ericsson title when Venus was still zigzagging in form as she made her way back from injury. The older sister said Sunday that her lack of court time after a long injury layoff last year left her 6-foot-1-inch frame without enough muscle to play in her accustomed style.
Then Serena got hurt midtournament at Wimbledon as Venus blasted through the draw to the championship.
"It was really difficult because I was on a roll and I felt like I was going to win Wimbledon," said Serena. "I felt like I was just going to do big things in the summer. I wanted to win [the U.S. Open Series,] where you can double your money here.
"I was really ready to play, and I felt like, you know, when I finally dedicate myself, this happens. So it was actually frustrating, and I had to get over -- mentally, I just had to, like, just pull myself back and be like, it's going to be OK, because it was really hard to have another setback was frustrating, to say the least.
Now, they seem to be peaking at the same time, which is extremely bad news for the rest of the field. The siblings dismantled their fourth-round opponents -- no slouches, either -- in straight sets with frightening ease Sunday.
Marion Bartoli of France, who lost to Venus in the Wimbledon final, was Serena's victim this time, managing only 10 winners in the 6-3, 6-4 loss. Although Venus' serving has drawn more attention, especially since she fired off a Slam-record 129-mph rocket a few days ago, Bartoli said Serena also has plenty of gunpowder.
"I almost just couldn't return it," Bartoli said. "I mean, when it's coming 125 miles or something, I don't even see the ball coming up. I can't see if it's middle or wide serve. It's coming so fast.
"She just elevates her game when she needs to. She's not obviously trying to play the hardest on every point. She just wait for the great moment, and then go for it and play some great shots when she really need to."
Venus has seemed almost preternaturally calm -- you might call it serene -- as she skims around the court in outfits branded with the logo of her new company, EleVen. She took time off after the U.S. Fed Cup loss to Russia the week after Wimbledon and played only one hard-court event this summer, but arrived in New York looking refreshed and in command.
"When I got on the court, I just wanted to not rush, and just take my time, and just go ahead and do what I needed to do, tell myself to just go ahead and take care of the job, if that makes any sense," she said after romping past fifth seed Ana Ivanovic of Serbia. "A lot of times, in my head, I just try to make it simpler and not let it get complicated, and just really enjoy hitting the ball."
Serena took the entire hard-court season off with a sprained ligament in her thumb, an injury trainers told her is more common in football than tennis.
"I would have preferred to have Pilot Pen or L.A. or at least one tournament under my belt going into this because I think it just makes it a little bit easier."
Yet she is following her usual modus operandi of using the early rounds as fitness training.
The sisters are tied this year in Grand Slam wins, one apiece. Their lifetime head-to-head record stands at 7-7. Nine of those 14 matches have come in Slams, including the famous cluster of five straight finals Serena won over Venus in 2002-03.
They're conjoined in every way except when circumstances put them on opposite sides of the net.
"Obviously, I want nothing but the best for her and she wants nothing but the best for me, unless of course we're playing each other," Serena said. "Then it's like, 'OK, I want to win.' That's how we look at it."
Bonnie D. Ford is a frequent contributor who is covering the U.S. Open for ESPN.com.