Tyson Gay may be missing, but Walter Dix believes he can take up the slack for US sprinting at the 2011 World Championships in Daegu, South Korea.

Gay's injury withdrawal, before the semifinals of the 100m, rocked the US athletics championships that concluded on Sunday.

After all, Gay was the only man to beat Jamaican Usain Bolt in 2010, and his American 100m record of 9.69 makes him the second-fastest man ever behind Bolt, who holds the world record of 9.58.

But Dix, who claimed a 100-200 double at the US championships, which served as the World Championships trials, vowed to be ready to take on Bolt - or anyone else - come August.

Dix had run just two other 200s coming into the US championships and only one 100m, and said he expected to be faster than his 100m 9.95 and wind-aided 19.95 in the 200m by the time the World Championships roll around.

"Nine weeks is plenty of time to get really, really fast," said Dix, whose 100m and 200m bronze at the 2008 Olympics made him the most successful US sprinter at the Beijing Games.

His hopes of improving on his Beijing bronze double at the 2009 World Championships ended with a hamstring injury at the US trials two years ago.

Since then, Dix says, he has matured.

"I'm stronger, I'm lighter, I'm smarter," he said. "I know what I'm able to do."

Gay won't be the only marquee name missing from America's World Championships team.

Hurdler Lolo Jones missed out on a berth, while pole vaulter Brad Walker and heptathlete Hyleas Fountain delivered sub-par performances that had their Daegu berths in limbo.

But a string of new names, including women's 200m champion Shalonda Solomon and 400m hurdles winner Jeshua Anderson, promised the United States will continue to be a force not only at the World Championships but also at the 2012 London Olympics.

Solomon, a junior world champion in 2004 and ranked No 3 in the world last year at 200m, earned her first place on a US international team as her 200m triumph denied Carmelita Jeter a 100-200 double.

"It's not like she doesn't have credentials," her coach, Lance Brauman, said. "She's just had some bad luck with some injuries... I wouldn't call it a surprise."

The women's 200m was wide open after Allyson Felix, the three-time defending world champion, opted to test herself in the 400m.

Felix won the 400, and could tackle the daunting double in Daegu.

Reigning 400m world champ Sanya Richards-Ross won't take on the same double.

Like Felix she bypassed her favorite event at trials, but finished seventh in the 200m so will compete only in the 400m individually in Daegu.

"I think we have a good combination, a good balance of veterans and youth," Team USA's men's head coach Vin Lananna said. "I think the United States is in a great position for the Championships in Daegu and also in setting the table for what's to happen in London a year from now."