Walter Dix, left, wins the men's 200 meters ahead of, from second from left, Darvis Patton, Justin Austin and Shawn Crawford, during the U.S. track and field championships. (Don Ryan/AP)

When Tyson Gay pulled out of the 100 and 200 meters at the U.S. track and field championships last week, black clouds all but settled over the American sprint world. Track aficionados lamented the loss of the only serious U.S. challenger to Jamaican Usain Bolt at the world track and field championships in Daegu, South Korea, this summer.

Walter Dix considered that thinking utter nonsense. After quietly wrapping up an impressive U.S. title double Sunday with a victory in the men’s 200-meter final, he boldly declared that he is the guy who will bring down Bolt.

“I want [Bolt] to be at his best, so when I beat him there will be no excuses,” Dix said.

Dix won a hard-fought victory in the 200 meters Sunday, crossing the finish line in a relatively pedestrian — and wind-aided — 19.95 seconds. He edged Darvis Patton, who finished in 19.98, two days after claiming the gold in the 100 with another narrow victory and rather ordinary time of 9.94. There he edged 2004 Olympic champion Justin Gatlin in a photo finish.

Yet Dix stood in bright sunshine on a practice field well after the Hayward Field stands had emptied and promised to run much faster in August, flashing the bravado and brashness that had been missing from the U.S. men’s sprint squad since Olympic great Maurice Greene last competed in 2008.

“I intend to come back with gold,” Dix said about Daegu. “I’m closing in real quick and real soon. Once I get really sharp, the times are going to come down quick. People are going to be shocked. . . . I’m going to train to run a 9.56 if [Bolt] runs a 9.57. If he runs a 19.19, I’m going to train to run a 19.18.”

Dix’s achievements at these championships were almost matched by Carmelita Jeter, who on Sunday claimed the silver in the women’s 200 two days after winning the gold in the 100. Shalonda Solomon passed Jeter in the last meters of the race, claiming the victory in 22.15 to Jeter’s 22.23. Jeter, who has run the second-fastest time ever in the 100, will be a gold medal favorite in both events in Daegu, but she will face heavy challenges from Jamaica’s stars and three-time world 200 champion Allyson Felix.

Shot-putter Adam Nelson, meantime, won his fifth U.S. outdoor title with a world-leading heave of 72 feet 53 / 4 inches, his best throw since 2008 and enough to secure him a berth on his sixth world championship team, matching the number of appearances by shot put legend John Godina. 

“I don’t even keep track of them anymore,” said Nelson, 36, a Dartmouth graduate who earned his MBA at the University of Virginia in 2008. “My last two goals in the sport are still the world record and an Olympic gold medal. The world championships is a stepping stone to one of those for me.”

Nelson will be joined in Daegu with Christian Cantwell (71-9) and Reese Hoffa (71-83 / 4), one of Nelson’s training partners in Athens, Ga. Each of the veteran trio has collected a world title in the past; Nelson has medaled in all of his previous world championship appearances except the last in Berlin, when he finished fifth. He doesn’t expect a down performance this summer.

“The last two weeks have been the best practices I’ve had since 2008,” he said. “Finally, things are starting to come around. I’m not a big power guy like some of the other guys. . . . I have to be on to throw far.”

Dix said his best practices will come in the next eight weeks. The former Florida State star won a pair of bronze medals at the 2008 Summer Games, but said he isn’t interested in bronze or silver in Daegu. Rey Robinson, Dix’s coach, said Dix trained to manage the physical toll of competing in six races here; he has barely dabbled in the speed training that will occupy the next eight weeks before the world championships. 

He skipped the indoor season to focus on strength training, and only entered three outdoor races before these championships: one 100 and a pair of 200s.

“I can’t predict what he will run” in Daegu, Robinson said, “but I can say that he will be a world-record holder in one of those events — the 100 or 200 — sometime soon.”

Dix has a personal best of 19.69 in the 200 and 9.88 in the 100, which make world-record projections seem like a reach, but he has frequently been under 20 seconds in the 200 and ran the 19.69 as a junior in college in 2007.

He said he could have performed better at the Beijing Olympics, but a hamstring injury leading up to the Games slowed his training. He missed most of 2009 because of injuries, but won the U.S. title in the 100 last year and got second in the 200. A few weeks later he defeated Gay in a wind-aided 200 race on this track.

“I always had confidence,” Dix said. “Last year when I beat Tyson, everybody was shocked. . . . I wasn’t shocked.”