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Usain Bolt set up a last date with a 100-meter final, and Justin Gatlin will be waiting there for him.

Bolt was again slow out of the blocks, came back strong and coasted to the line. But that was only good enough for second in his world championship semifinal heat behind Christian Coleman on Saturday. The American won the heat in 9.97 seconds, .01 seconds ahead of the Jamaican great.

Bolt, who has been struggling with form for much of the season, hasn't had a strong start yet at the Olympic Stadium, and it could cost him in the final.

Still, Bolt and Coleman were the only two sprinters to break the 10-second mark, with 2011 champion Yohan Blake winning his semifinal heat in 10.04 for third fastest.

Even though the 60,000-sellout crowd was shouting "Usain Bolt, Usain Bolt," the multiple Olympic champion was subdued by his standards, showing little of the flashy hyperbole that has marked his greatest moments.

Two years ago, Bolt just held off Gatlin in the world championship final. The 2004 Olympic champion also finished second in his heat on Saturday, behind Akani Simbine. The South African had a time of 10.05 seconds, an edge of .04 seconds over Gatlin.

Other finals on Saturday are the men's discus and long jump, and the women's 10,000. Earlier, there was another runner who put on a show that was almost vintage Bolt.

Slow start, work your way up, and at the end look left and right before coasting first across the line in a jog.

This time it was Wayde van Niekerk winning his opening heat in the 400, his first race of possibly six in as many days at the world championships. The Olympic champion crossed in 45.27 seconds, .26 ahead of Nery Brenes of Costa Rica.

Like Bolt, a rival setting off faster no longer phases him. Van Niekerk just made sure he produced some extra power on the final straight to rein in Brenes.

Van Niekerk is seeking to win gold in both the 400 and 200 meters over the next week. He is tipped by many to become the sport's next star now that Bolt is retiring after the world championships.

In both races, though, he might find his toughest rival in Isaac Makwala of Botswana. Makwala was just as good in his heat. Following a fast start, it was a jog in the finishing straight as he finished in 44.55 for the top time of the day.

The two are equally tight competitors in the 200, too, yet there is no bitterness in their rivalry.

"Wayde van Niekerk is my brother," Makwala said. "We want to conquer the world together and make the final for Africa. He is so friendly and a lovely guy."

The two-day heptathlon also started and after two events Olympic champion Nafi Thiam took the lead. She scaled 1.95 meters in the high jump to reach a total of 2,215 points.

In a battle of 22-year-olds, Yorgelis Rodriguez matched Thiam in the high jump with an incredible 8-centimeter improvement of her personal best to keep in touch in the overall standings with 2,207 points. Caroline Schafer of Germany was third with 2,165.

One of Thiam's toughest rivals, Katarina Johnson-Thompson, only cleared 1.80 in the high jump, well short of her best of 1.98, to dent her gold-medal hopes. She was in fifth position with 2,053 points.

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More AP track coverage: https://www.apnews.com/tag/London2017