Justin Gatlin, in his first U.S. track and field championships since testing positive for a banned steroid five years ago, finishes his preliminary 100 meters heat in Eugene, Ore. Gatlin won in 10.08 seconds to advance to Friday’s semifinals. (Don Ryan/Associated Press)

As eight men lined up for the first heat of the 100 meters at the U.S. track and field championships Thursday, the Hayward Field announcer tried to pump up the crowd, telling fans in a booming voice to “take note” of two Olympians stepping into the blocks below. He named Shawn Crawford and Darvis Patton.

He left out the biggest star of all, the 2004 Olympic 100 champion who stood with narrowed eyes, gnawing on chewing gum, in Lane 8. He did not mention Justin Gatlin until he had to, when Gatlin got out to an early lead and then cruised to a victory in 10.08 seconds to advance to Friday’s semifinals.

In his first U.S. championships since he tested positive for a steroid five years ago, earning a four-year ban from competition, Gatlin has been fighting hard on two fronts: to get his legs to churn like they did when he was 24, and to convince the international track world that it should welcome him back.

“With each race I have, I build more confidence,” said Gatlin, 29, who needs a top three finish in Friday’s final to win a spot on the U.S. team that will compete at the August world championships in Daegu, South Korea. “I’m just grateful that my competitors have been very gracious to me and helped me come back. I just want to be the best I can be.”

As he tries to reclaim his old speed and reputation, he has found that athletic excellence isn’t at his fingertips like it once was, and respect from the international track world cannot be taken by force.

He continues to be barred from all of the major professional meets in Europe because of his connection to doping, even though anti-doping officials have defended his right to compete. He still denies intentionally consuming any banned drugs even while apologizing profusely for a positive test that was announced just weeks after he set the 100 world record of 9.77 in May 2006.

“Anything I’ve done that is a black eye or embarrassment, I give them my utmost apology,” he said. “I just want to come out” and run.

His positive test wiped his world record off the books, but it’s been obliterated many times over, anyway. Jamaican Usain Bolt lowered the mark to 9.58 last summer and Tyson Gay, who also advanced in his heat Thursday with a finish in 10.01, has run an American-best 9.69.

Gatlin said he officially returned to the sport at a handful of minor meets last summer with so much deference “I felt like I was running for mayor or something.” This summer, he said, he wants to get his killer instinct — and speed — back.

“I love having him back,” Crawford said. “I feel like if you’ve served your time . . . when you come back you should be allowed to compete like anybody else. He won his heat today. That’s a good start.”

With so much at stake, Gatlin wanted to be in top form here, challenging for individual spots in both the 100 and 200, which will be contested beginning with Saturday’s heats. Yet he has been frustrated by slight injuries to his quadriceps and hamstring and an untimely bout of strep throat that slowed his training.

“I’ve had a lot of bad timing lately,” he said. “I just need quality races with quality runners. Once I’m 100 percent healthy, I’ll be able to produce the times I need to produce.”

Three weeks ago at the Prefontaine Classic on this track, he ran a sub-10 second 100 for the first time since 2006. But his time of 9.97 was good enough for just sixth in the race, which Steve Mullings won in 9.80. Ivory Williams and Michael Rodgers advanced Thursday in 9.95, the best time in the heats.

“The stuff I’m doing in practice calculates to 9.8s or high 9.7s,” he said. “It’s just putting it together on the track and in a race. It can be done.”

During his time off, Gatlin became a father and his son Jace Alexander, who just turned one, has given him an unexpected inspiration. He not only wants to provide for him, but he also wants to inspire him.

“I want to give him something to look forward to in the future,” Gatlin said. “I don’t want him to carry a last name and not be proud of it.”

Notes: Galen Rupp began the men’s 10,000-meter final late Thursday wearing a black mask to filter pollen from the air but ditched it before separating himself from a packed lead group over the last lap to win his third straight U.S. title at the distance. With a last lap of 54.4 seconds, Rupp won in 28 minutes 38.17 seconds, topping Matt Tegenkamp (28:39.97) and Scott Bauhs (28:40.51).

Shalane Flanagan dominated the women’s final, separating early and winning in 30:59.97, crushing Kara Goucher (31:16.65) and Jen Rhines (31:30.37).