The 23-year-old Neugebauer, who arrived ranked 13th in the world, had 4,640 points after the 100m, long jump, shot put, high jump, and 400m.
“You can never be unhappy, especially when you did such an amazing job during a first day,” Neugebauer said.”The decathlon is like a marathon and we are only halfway there.”
“I have to go event by event. I will try to beat myself, my personal bests. If that is enough for a medal or even a gold, that would be great.”
Canadian Pierce LePage, the silver medallist at last year’s worlds in Eugene, overtook his teammate Warner with a solid 400m to sit in the silver medal position with 4,610 points.
Warner, who has world silver and bronze medals to go with his Olympic gold, ended the day with 4,578.
World record holder Kevin Mayer of France withdrew after the long jump, having suffered an Achilles injury two weeks ago.
“Since (the injury) I had eight hours of physiotherapy every day. I was not able to train at all. I knew it was going to be difficult but I tried,” said Mayer, who was 15th when he pulled out.
“When I realised my left leg was starting to hurt more and more, I decided to stop. I knew I would not finish the decathlon and I wanted to stop before it becomes a big injury.”
Strong start
Warner, who led last year in Eugene before pulling up with a hamstring injury in the 400m, had a strong start to lead after the 100m and long jump on Friday.
But Neugebauer, who was 10th at last year’s worlds, overtook the Canadian with personal bests of 8.00m in the long jump and 17.04m in the shot put.
“I don’t think I can complain too much this year,” Warner said. “Last year I was walking through these stands with tears in my eyes because I wasn’t able to finish day one.
“I get to start day two this time, and I’m in a good position, so it’s all a bonus.”
“I’ve just got to follow my gameplan and hopefully it lands me on top of the podium. We’re going to have to battle the heat tomorrow too, so it’s not going to be easy but we’re decathletes at the end of the day and we’re meant to be tough men.”
LePage climbed into second place with his time of 47.21s in the 400m, while Neugebauer’s 47.99s was just enough to keep him in the lead overnight.
Day two on Saturday features the 110m hurdles, discus, pole vault, javelin, and 1,500m.