Dortmund - Athletics legend Usain Bolt insists he is serious about realising his dream of becoming a top-class footballer after training with Borussia Dortmund.
"I really want to try and make it professionally, to play at a high level," the sprint superstar told reporters on Friday at the German league club.
"My goal is to make a top team and play in one of the top leagues in the world."
Nearly 200 journalists and around 1,500 fans saw the eight-time Olympic gold medallist put through his paces with the first-team squad at Dortmund's training ground.
Having already trained with the team behind closed doors on Thursday, Friday's open session could be seen as a publicity stunt as both Bolt and Dortmund are sponsored by Puma.
The Bundesliga club live-streamed the training session and in China alone 1.2 million viewers tuned in.
The 31-year-old Bolt insists he is deadly serious about starting a new career - at an age when most footballers are hanging up their boots.
Bolt, who retired from athletics last year, admits he lacks the endurance fitness football demands.
"Overall, I'd give myself a seven out of ten," he said.
"It was fun, the guys were cool and they were welcoming, but I can tell I was unfit.
"I like to play on the wing, right now I am unfit so I try to stay up top (as a striker).
"I've heard a lot about the fans here - that really was an experience."
As expected, Bolt, the 100m and 200m world record holder, showed phenomenal pace over the turf.
He was proud of the header he scored in a practice game, but admits having much to learn.
"I'm tall, so it's one of the things I have practised over the years," he said of his header with sweat pouring down his face.
"I was working hard out there, I wanted to play my best, move and give the guys options."
Dortmund coach Peter Stoeger gave a realistic appraisal of Bolt as a footballer.
"He is talented, but if he wants to make it at the top level, there are still a few things to do," said the Austrian.
"It's a big leap from athletics to football.
"He's an unbelievably laid-back guy, an athlete with so much success, but with his feet very much on the ground.
"He had fun and he got some feedback, which was his wish.
"He understands the game, what he's missing is the team work and how to move."
Bolt wants to be invited back to train again - and maybe even sign - with Dortmund.
"I hope to come again and hopefully they will welcome me, I can get better and (they'll) sign me - you never know," he said.
The Jamaican refused to measure himself against Dortmund's professionals.
"I don't compare myself to them yet. I want to play at the level I know I can, to improve and to learn from them," he said.
"This is what they do for a living and I am trying to get into this by watching and learning."
However, he was very clear that he does not want to play lower league football.
Bolt dismissed even the suggestion of playing for Dortmund's reserves in Germany's third division to gain experience.
"I wouldn't want to play in a lesser league, I want to play in the top league - this is why I am here," he added.
"I would like to work with the team more and improve my skills, get better and try to play in the big league.
"I don't set any standards, I don't know where I am at.
"If it gets to the time where I feel like I am at the level, then the coaches or the club will say 'alright, you know what? You can play at this level or that level'
"Until then, I am just going to working hard and pushing myself."
Bolt, a Manchester United fan, is already due to play at the club's iconic Old Trafford stadium in a charity football match on June 10.
Bolt will line up opposite British pop star Robbie Williams and captain the Soccer Aid World XI in a match to raise funds for the United Nations Children's Fund, Unicef.