Rio de Janeiro: Usain Bolt and Justin Gatlin warmed up for their 100m Olympic showdown on Saturday with easy victories as German discus thrower Christoph Harting claimed his brother's crown.
Bolt and Gatlin are poised for the final chapter of their long rivalry on Sunday when they are expected to duel once more for the title of fastest man on the planet.
The two sprinters easily negotiated their opening heats on a raucous morning session at the Olympic Stadium, with Gatlin topping the qualifying times with a tidy 10.01sec.
Jamaican superstar Bolt, bidding to win 100m, 200m and 4x100m titles for a third straight Games, was fourth quickest in 10.07sec.
Afterwards, Bolt said he was pleased to have got off the mark without any problems.
"I'm feeling good. I'm happy. As I said, I've got the first one out of the way so I'm happy about that," Bolt said, predicting a fast semi-final.
"It's definitely going to be a good semifinal. There are a lot of guys running fast. It's good. It gets you running and gets you up to speed to go out there in the finals."
Gatlin, one of the oldest men in the field at 34, said he was kept on his toes by a crop of young sprinters.
"These young guys coming up, it's a different breed," he said.
"They're running with their heart, they're trying for the finish line and going for that podium."
Gatlin, who has twice been convicted of doping offences, has faced criticism from even within his own team at these Olympics, with teenage swimming gold medallist Lilly King saying last week athletes like him should not be allowed to compete.
But Gatlin bristled when asked to respond to the young swimmer's remarks following his race.
"I don't even know who Lilly King is -- she does swimming, not track and field. I'm not worried about that," Gatlin said.
"I've come back and done what I need to do. I've worked hard to get back to here, I've been tested like everyone else and I believe in the system like everyone else," added Gatlin, who served a four-year ban for the second of his two doping offences.
The morning's only gold medal went to Germany's Harting, who saved his best for last to win gold.
It was an emotional win for Harting, whose famous shirt-ripping brother Robert -- the 2012 gold medallist --failed to qualify for the discus final in Friday's preliminary rounds after suffering a back strain.
Harting took gold with a personal best of 68.37 metres on his sixth and final attempt.
Poland's Piotr Malachowski took silver with 67.55m and Harting's teammate Daniel Jasinski bronze (67.05).
"You have moments in your life when you focus completely," Harting said of his winning throw.
"I said to myself that no one's going to take that victory away from me."
Meanwhile the battle for the heptathlon crown is poised to go to the wire after Belgium's Nafi Thiam edged into a five-point lead over Britain's defending champion Jessica Ennis-Hill following the morning's long jump.
Thiam leaped a best of 6.58 metres to leave her up front on a total of 5,018 points. Ennis-Hill only made 6.34m for 5,013 to increase the pressure going into the final two disciplines of the gruelling event, the javelin and the 800m.