Team GB sprinter Louie Hinchliffe laid a marker down in his 100-metre heat on Saturday, beating American star Noah Lyles with a time of 9.98 seconds.
Hinchliffe, who hails from Sheffield, impressed in the third heat of the day and ran just below his personal best of 9.95s. He advanced to the semifinals with the third fastest overall time.
Lyles was relatively slow out of the blocks but came back to finish second with a time of 10.04s, ahead of South Africa's Shaun Maswanganyi, who ran 10.06s.
"It was good to get him back after London, it was a good feeling. I wasn't really thinking too much about him, he wasn't really near me, so I wasn't really thinking too much about who was in the race," Hinchliffe said.
"I think the pressure and environment will bring more out of me, trying to get to an Olympic final. I'm just running my races at the moment, I'm not really thinking too much about results, I don't really want to chase results."
Zharnel Hughes joined Hinchcliffe in the semifinals with a time of 10.03s in the final heat of the day.
"I just got through the round, that's all I needed to do. I'm okay with it [the performance]," Hughes said.
"I could have gotten a better start, I was a bit lazy in the start because the false start kind of threw me off a little bit so I just needed to stay relaxed. I knew I could pull through because I have one of the top ends in the world, so I just needed to relax.
"It almost sounds like football is going on inside here. Anytime you stand outside a football stadium you can definitely hear the crowd. It's so lovely to hear the fans being here, the support when you come out is absolutely amazing."
Earlier, Welshman Jeremiah Azu was left heartbroken after he was disqualified for a false start in the day's first heat.
Azu argued his case with officials before he was forced to leave the track, unable to race under protest.
"I'm feeling great, so it's a shame. There's a lot of crowd noise, the pole vault is going on. I reacted to a sound and they've said I can't run under protest," Azu said.
"It's an Olympic crowd, they are all so excited, I don't fault them but we are on the start line, someone has reacted to something and it's set me off."