BOSTON - The perfect 10 has been replaced, at least for now, by the imperfect 17.05.

It doesn't have quite the same ring, but Nastia Liukin's score on the uneven bars at the U.S. championships last night had just as much impact as that rounder number. Put it this way: If the lithe Russian-Texan gymnast can match that performance in Beijing in two months, she'll be on the medal podium.

"Finally getting a 17 on the bars was amazing," said Liukin, who fell during her floor exercise, her first routine of the night. "I was a little bit upset after floor, but then I had that 17."

Under the new gymnastics scoring system, Liukin can actually score significantly higher. Her bars routine comes with a monstrously high start value of 7.7 points. Her second score, for execution of the routine, was a good but imperfect 9.35.

"I think she can get [the execution score] to 9.5," said her coach and father, Valeri.

Liukin's perfect-10-plus-7.05 did more than vault her from 12th place to second in the overall standings. It also raised the temperature of her friendly (honest!) rivalry with the effervescent Shawn Johnson.

One of these two will be That Girl, the face of Team USA in the 2008 Olympic Games. Liukin, 19, had been on track for that distinction until the 16-year-old Johnson's explosive debut on the senior level last year. Liukin competed with an injured ankle while Johnson won everything in sight, including the all-around gold medal at the world championships.

In March, a healthy Liukin defeated Johnson at the Tyson American Cup in New York. Much was made of Liukin's return to form, but in reality the outcome was decided when Johnson fell in her first competitive attempt at a new, high-scoring vault.

So the Celtics and Lakers weren't the only old rivals going head-to-head again in Boston.

Johnson set the tone. She was the first performer of the evening on the floor - a brand-new piece of equipment identical to the surface in Beijing, but different from the ones the gymnasts typically practice on.

Johnson was performing a new routine for the first time. She said she was nervous in her first competition since the American Cup. It didn't show.

"I was talking to myself a lot," Johnson said. "I was telling myself to calm down. I didn't feel like myself. It's been a few months since the American Cup."

Johnson put up consistently strong scores and was first overall at the end of the night. Liukin had that fall on the floor and a solid, unspectacular vault, so she drifted down to 12th overall going into that uneven bars routine.

When the score flashed, there was little reaction from the crowd. That 17.05 just doesn't have the same cachet of the perfect 10.

Johnson knew what it meant, though.

"I honestly was really excited," she said. "I was thrilled. I give Nastia so many props for having such a hard routine."

Johnson and Liukin always compliment each other's performances. They really do seem to get along. They may not be "BFF" or anything, but Johnson says they regularly send each other text messages when they're not together. If that isn't the 21st century definition of pretty good pals, what is?

But the competition is real enough, too.

The 17.05 "made me want to work even harder so that I could keep the lead," Johnson said.

The competition picks up tomorrow. The scores from both sessions will be combined to determine the national champion. The top 12 all-around gymnasts will advance to the Olympic trials at the Wachovia Center June 19 to 22. They will be joined by a few top gymnasts who are returning from injuries.

Truth be told, winning the national title is not nearly as important to the Big Two as continuing to prep themselves for Beijing. Liukin and Johnson would have to sucker-punch a Karolyi to be left off that six-person team.

"I'm not at 100 percent," Liukin said. "I want to be at 100 percent later in the summer. You just have to pace yourself. Everything [this meet, the trials, the selection camp in July] is so close together, and you want to be 100 percent ready at the Games."

Liukin's image will grace NASCAR driver Jeff Burton's car this summer. Her new Visa ad will debut this weekend. Johnson is aligned with Coca-Cola and McDonald's.

They are both capable of winning gold medals.

They are both capable of winning some hearts, too.

Liukin is taller and more graceful, Johnson is compact and powerful. Liukin is a ballet dancer, Johnson a pop star. They both have star power.

Either could be that perfect 10, if there was such a thing.

Contact columnist Phil Sheridan

at 215-854-2844 or psheridan@phillynews.com.

Read his recent work at http://go.philly.com/philsheridan.