The 24-year-old dragged his trailing leg on the final hurdle in Stockholm in August to finish in a world-leading 46.87 seconds -- 0.09 seconds shy of Kevin Young's world record, a mark he has inched ever closer to throughout his career.
"I was really, really happy of course with the race in itself. But stumbling into the last hurdle and just looking at the time, knowing that most likely I spoiled my chances of a world record right there ... I think I've never felt that way before."
Young's world record, set at the Barcelona Olympics, has stood for 28 years, the longest-standing record in men's track running.
Warholm has run four of the 10 fastest times in the event's history, while his two closest rivals, Rai Benjamin and Abderrahmane Samba, make up the only other athletes to ever run under 47 seconds.
Between those three, the race for the world record is very much on.
"This is going to be really, really tough competition-wise," says Warholm, who took the world title ahead of Benjamin and Samba last year.
"I think in 400m hurdles we are in for a real treat because everybody wants this right now. I think it's going to be like the moon race between the United States and Russia -- it's going to be crazy."
"It's really important to have competition, somebody pushing you and somebody keeping you on your toes, I really like that," Warholm adds.
"I'm thankful for my competitors -- even though I want to beat them, of course."
Quality training and being best friends with the coach
Warholm, who originally competed in decathlon, achieved a major breakthrough when he won gold at the 2017 World Championships in just his second full season as a 400m hurdler.
The then-21-year-old's reaction to that victory was iconic, clawing his fingers down the side of his face with his mouth agape in disbelief. He had run hard and fast straight from the gun, a trademark of his performances over the years.
An expressive persona has become a common feature of Warholm's races, too. The Norwegian will thump his chest and roar words of self-encouragement as he's introduced to the crowd on the start line -- psychological preparation for what lies ahead.
"When I look at my races, I get sort of embarrassed because it looks silly, but at the same time it works for me and it's a part of my routine," says Warholm.
"When I'm in training I only race against myself and the clock. I'm just trying to get that adrenaline and trying to get the high quality. I started it in training, getting psyched up by hitting myself and everything and for me it just works.
"It's important to train with really, really high quality, and I think that is one of our secrets -- we train with almost the same quality that we do in competitions."
Warholm often speaks about his success in plural, rather than singular, terms, sharing the credit with his coach Leif Olav Alnes. The pair started working together in 2015, after Warholm was told Alnes is "the greatest coach in Norway and probably also the world."
Despite Alnes being nearly 40 years Warholm's senior, the pair have forged a strong friendship away from the track.
"He's worked with a lot of great athletes in Norway and what I like most about him is his knowledge," says Warholm.
"He is very, very well educated. He's really smart. But at the same time ... he speaks in very understandable terms.
"I really like hanging out with him and sometimes I hang out at his house, just talking. We are like best friends. I really enjoy spending time with my coach, and I feel it's also a secret behind our results -- we really communicate very well.
"I think people underestimate the value of being on a mission together and working as a team, (even) in an individual sport that track and field is."
Mastering the man killer
Warholm's multi-sport background saw him compete in events across the track and field spectrum in his teenage years. He occasionally doubles up in disciplines today, and after running the fastest 400m hurdles time of the year in Stockholm, he returned to the track hours later to win the 400m flat.
"I'm all in for the 400m hurdles," he says when asked if he'd consider taking on other events in the future.
"But, at the same time, I've always thought that I want to try other events down the road, even if that's 400m flat or 800m.
"Right now, it's all about the 400m hurdles because I feel like we're on a mission there and there are things I want to achieve when it comes to that event."
There are few disciplines in athletics more demanding than the 400m hurdles, an event that requires a unique blend of speed, strength, endurance, flexibility and technique, plus the determination to push through the pain of the final 100m.
"When you get nervous before the 400m, that is the reason -- the last 100m," says Warholm.
"You know it's going to be tough but at the same time that is what makes it so tough because everybody else feels the same way. Who can deal with it best and who is most fit for the event?
On top of managing periods of quarantine and coronavirus testing, Warholm also overcame a stress fracture in his leg at the start of the summer before enjoying the best season of his life.
He now has a chance to gradually build up his training again ahead of a year that includes the rescheduled Olympic Games. But Warholm refuses to put a number on what he wants to achieve in 2021.
"My main target has always been and hopefully will always be to develop myself and become even better," he says.
"There are big chances that I'll be even better in 2021, but when it comes to championships anything can happen. That is what is fascinating about sport -- if they handed out the medals before the race was run it would be boring."