You would have been hard-pressed to realise a game was going on at the Nicolau Alayon stadium if you were in that area of Brazil on August 8 last year.
The ground, also known as Comendador Souza, is tucked away between factories just a few minutes from Barra Funda, one of Sao Paulo's busiest transport hubs.
Just 203 fans paid less than €5 a ticket to see Nacional host Ituano that day, with the visitors handing the then 17-year-old teenager Gabriel Martinelli his first start for the senior team.
It looked destined to be just another midweek game under a cloudless sky, but Vinicius Bergantin still has vivid memories of what happened.
A former centre-back for Hannover 96, Bergantin watched his team lose 3-1, but it was a post-match conversation with the Brazilian wonderkid that stuck in his mind.
"The match had ended around 5 p.m., and I was surprised to find Martinelli already showered and dressed in the dressing room 10 minutes later. Most of the players had not even taken their kit off. And there he was with his bag on his back," Bergantin tells Bleacher Report.
"Suddenly, he came to me saying he needed to talk. I called him aside, and then he asked me if he could leave the stadium with his father. Normally, our rule is that everybody leaves together on the team coach.
"I was curious to find out why he was in such a hurry. And he explained to me that he had a class at 7 p.m. that evening.
"Perhaps, it may sound like an ordinary thing abroad, but to see a kid of his age making his debut in a tournament and not looking for a reason afterwards to skip school, claiming maybe that he was tired, is not really common in Brazil.
"He's so special that everything he does, he does well. From that, you can figure how far he can go—these are the actions of someone who knows what he wants in life."
Martinelli knows what he wants, and he definitely wants it fast.
It's now almost a year on from that game, and the prodigious forward can no longer be found in an Ituano jersey.
He's risen meteorically through the ranks, going from Brazil's fourth tier to the Premier League.
And Martinelli is already looking comfortable in Arsenal colours after completing a £6 million earlier this summer.
He made a big impact in his first appearance for the Gunners as he scored a chested goal against Colorado Rapids in the opening fixture of their pre-season tour across the United States.
A few days later, coming on as a substitute, he caught the attention of fans by showing an explosive burst of pace to slice in behind the Fiorentina defence from inside his own half, only to narrowly fire his shot wide.
The Londoners beat competition from a host of top sides to secure his services, including Barcelona and Manchester United.
One of his representatives even claimed to have received contacts from 25 different teams.
But for Martinelli's father, Joao Carlos, it wasn't solely a matter of accepting the highest offer on the table. He also wanted to hear what the clubs had planned for his son's future. And Arsenal ticked most of the boxes.
His main concern, above all, was to make sure Martinelli didn't become one of those up-and-coming prospects who move to the Premier League hoping to make the grade only to then be repeatedly loaned out to smaller outfits, eventually departing without having made a competitive appearance.
He was assured Martinelli wouldn't be a new Wellington Silva, a once highly-rated Brazilian winger who failed to play a single competitive second for the Gunners.
"Several clubs interested in him showed up [in the past months], but we didn't want to turn it into an auction. Others might think it was all about money, even though that was not what happened with Gabriel—we received higher bids for him," Joao Carlos tells B/R.
"However, we've got a verbal agreement with Arsenal that he won't be loaned out straight away.
"They have a plan for him and are expecting to see him reach his peak within one to three seasons. It would have been no use picking an offer, say, £10 million higher, if he did not get a proper chance in the end to grow. I have no doubt that he'll develop further training with the first team.
"I believe that in six months' time he'll be delivering the goods."
The buzz around Martinelli began to emerge in January after he netted six times in four outings during the Copa Sao Paulo, the most prestigious youth competition in Brazil.
He didn't stop there, though: Brought back to the senior squad, he led Ituano to the quarter-finals of the Sao Paulo State Championship, with an impressive record of six goals and three assists in 14 appearances.
That helped him earn the best newcomer award and also a spot in the team of the tournament.
A few weeks later, he was included in a group of youngsters invited for a training camp with the senior Brazil squad, working alongside Neymar, Gabriel Jesus and other stars ahead of the Copa America.
It was clear that Arsenal had to move quickly to snap Martinelli up. At the beginning of the year, the Gunners weren't exactly in pole position for his signature.
Back then, following a 2-2 draw between Ituano and Corinthians, they enquired about him and were told "he was close to a move to PSV Eindhoven." The Dutch giants had no doubt about his potential and wanted him to follow in the footsteps of Romario and Ronaldo in the Eredivisie.
Arsenal continued their talks, but it took them a few more trips from club scout Everton Gushiken to come to the conclusion that they couldn't let Martinelli slip away from their hands. Ultimately, they decided to bid, and a verbal agreement was reached in late April.
The boy with a school bag on his back had become the first arrival of the summer for a team desperate to reinvent itself.
A skilful forward who is blessed with lightning pace, capable of finishing with both feet and possesses a work rate that often sees him dominate the flanks, Martinelli will be aiming to upset the odds and make a name for himself right away.
He may be young, but a move to Europe has long been in his plans. "He was sort of raised for this world since the age of six," his father reveals.
Now, at 18, Martinelli has got an entourage almost as large as Neymar's when he first moved to Barcelona, comprised of professionals from different areas. He also shares the same sports agency with Vinicius Jr. and other promising stars. In a way, every step he took in his career was calculated to bring him to this stage.
He's considered so mature that his own team-mates struggle to believe his age.
"He stands out for his attitude on the pitch—when you watch him play, you get the impression he's been around for a long time. And then you realise he's still a boy and has ridiculous potential," former Dynamo Kiev midfielder Carlos Correa, one of his mentors, tells B/R.
"Within a short time, I think he will be on the top with the best players.
"He's a one-of-a-kind boy, well cared for and well educated by his family. He has a very positive inner circle. He listens a lot and talks little."
Throughout his time at Ituano, Martinelli progressed under the tutelage of the Middlesbrough legend and World Cup winner Juninho Paulista, who worked as the club's manager for almost a decade. The former midfielder witnessed his protege blossom into a confident forward.
One of the best Brazilian success stories in the Premier League, Juninho did not have it easy, but he paved the road for others.
"It doesn't take long to notice a player of his calibre," says Juninho.
"He has a big character, always tries to play the same way, whether it's against great teams or smaller ones. I've told him to carry on and maintain his playing style—driving the ball forward quickly and skillfully and finishing his plays accurately."
Martinelli has set his sights high. He models his game on five-time Ballon d'Or winner Cristiano Ronaldo. The Portuguese superstar has been his inspiration for many things in his career, including his diet and fitness routine. Despite being so young, he has learned to avoid the temptation of drinking soda.
"He has always followed Ronaldo's example," Joao Carlos says. "It's not a secret that Ronaldo can only perform at this level nowadays because he has taken care of his body.
"We always remind Gabriel that he's privileged for having such a talent, but if he doesn't work hard, he will be just another player on the pitch."
Martinelli is still an unproven footballer, but if there's one thing that he shares with Ronaldo, it's his mentality during training.
With the experience of having worked with him from the under-15 age group to the senior team, Ituano's assistant coach Luiz Antonio can safely attest to that.
"He was a boy that, you could see, wanted a lot [to reach this level]. He's always been aware of his potential, but it has never stopped him from leaving everything in training. He's a bit similar to Ronaldo in that sense," the former striker tells B/R.
"I lived in Finland for 18 years and have been following Ronaldo's journey since the very beginning. Martinelli reminds me of him a little when he's dribbling at speed, his ability to unbalance a game. But, obviously, when Ronaldo arrived [at Manchester United], he had come from a stronger league, playing for Sporting CP. It won't be easy for Martinelli.
"He naturally has a lot of work ahead of him. However, it's not like he needs to fix many things on his game—it's more a case of polishing."
Between 2015 and 2018, Martinelli was invited for trials at Manchester United and Barcelona on more than one occasion.
They were both seduced by his goalscoring prowess—he reportedly notched almost 200 goals in youth football.
When it comes to bulging the net, as one of his first coaches, Thiago Badari, puts it, "there's no ugly goal for Martinelli; ugly is not to score a goal."
"My memories of him are not those of a skinny boy, but of a bright youngster who was very intelligent reading the game, had an outstanding technique, a highly-competitive mentality. He was always pushing the ball forward, rarely missing it. He did things that left everybody incredulous," Badari, who currently works at Red Bull Brasil, tells B/R.
"He had an impressive nose for the goal, scoring in all forms—with his right foot, left foot, toe-poke, head."
At Arsenal, Unai Emery will have to put a lot of thought into the most effective way of bringing the best out of Martinelli since there doesn't seem to be a consensus even among his former coaches on how to use him.
"He has played everywhere in the attack, but I prefer him wide open on the left wing, although he can still play on the right side, too. He's very good driving the ball at speed, cutting inside and finishing," says Luiz Antonio.
"His futsal education helps him a lot getting past opposition defenders."
Badari adds: "Personally, I prefer him as a No. 10—he has amazing ball control, a great skills repertoire, I really enjoyed him playing in the midfield back in my days. But he also feels comfortable in small spaces and can perform as a second striker, a false nine."
Bergantin mentions the comparisons to Juninho, another graduate from Ituano, to try to settle the debate: "It's inevitable to compare them. But I usually saw Juninho playing more inside in the past while Martinelli prefers to be on the flanks. Both of them have the dribble, the ability to improvise. Apart from this, though, they are not really the same kind of player."
Alongside his wife and daughter-in-law, Martinelli's father will be travelling to London to help his son settle to life as quickly and smoothly as possible.
He will stay by his side as long as necessary to make sure the Brazilian sensation remains that same boy with a bag on his back who he took to school after his first senior game a year ago.
"Everything some of those famous players do, I hope he does the opposite. Sometimes, you get the feeling that these people think they can do everything because they have money. That's not how I raised Gabriel to be. We are what we do on our daily routines. He will treat everyone equally—from the kit man to rivals," Joao Carlos tells.
"I don't ever want to see his name involved with women or tax fraud cases in the media."
Instead, Joao Carlos has a different dream for his son that he hopes will happen sooner rather than later.
"I've always dreamed about watching him playing in the UEFA Champions League. Since he was a kid, I've talked to him about that—seeing him in Europe, walking up the stairs to the pitch with that Champions League song playing. I don't know if I'll be able to handle. I'll have a fit," he says, laughing.
Follow Marcus on Twitter: @_marcus_alves