It was not a one-off flash. In early March he took the ball past Nicolás Otamendi at Benfica's Estádio da Luz, left the veteran on the turf and finished past Anatoliy Trubin. Teammate Samu Aghehowa's reaction, relayed by A Bola, was a grinning "You have no mercy".
The record book had been filling up since Białystok. Pietuszewski scored for Jagiellonia at 16 years and 11 months, was named the Ekstraklasa's Young Player of the Month in both August and September 2025, and became the youngest scorer in the history of Poland's Under-21s.
Those who coached him early describe the same boy. Rafał Muczyński, his first coach, remembered a player who "always had a winner's character and took it hard when something didn't work out".
Rafał Lasocki, who handed him minutes in Poland's Under-17s as the only player from a younger age group, saw the talent at once.
"It was clear he was an exceptional talent," Lasocki said. "He is an exceptional person too, but not an easy one to lead."
He added that Pietuszewski had come back from a cruciate ligament injury "stronger, tougher and better than before", and "takes responsibility onto his own shoulders in difficult moments for the team".
Marek Wasiluk, his youth coach at Jagiellonia, put it more bluntly: "One of the best boys in Europe in his age group."
By the time Adrian Siemieniec was handling him in the first team, the questions were different. Siemieniec admitted in an April vlog interview that he had no template.
"I was working with a player like Oskar for the first time in my life," he said. "It's not that I knew what had to be done. Sometimes, when you don't know what to do, don't do anything. Just that."
In July 2025, with Pietuszewski 17 and 23 first-team games old, Siemieniec laid out his approach on the Foot Truck channel.
"He needs to experience success and get burned, experience the bench and see what it means to be left out of the squad," he said. "He needs a telling-off from an older player, criticism from the coach, but also support."
Teammate Afimico Pululu told O Jogo that the teenager never looked like a newcomer.
"He wasn't shy, it seemed he'd been with us for three years," the striker said. "Everyone knew from the first training sessions that he wouldn't stay with us long, two years at most."
It was barely a year. Porto paid a reported €8 million, rising to €10 million with add-ons, the highest fee ever recorded in the Ekstraklasa, with Arsenal, Manchester City and Chelsea all reported to have sent scouts.
Robert Lewandowski, the Poland captain, had a plea for everyone watching. "He is undoubtedly spectacular, but let's give the lad some space. Let him develop, let him play."
On the pitch, Pietuszewski is a left-sided winger who wants the ball and wants to take defenders on. Pace, close control and a willingness to try the difficult dribble are the foundation, and the Otamendi goal was all three at once. He is not merely a runner either: last August he equalised against Cracovia with a long-range strike in the 19th minute before winning a penalty in a 5-2 win.
Pepe, the former Porto defender, said he could use both feet.
"He is a very talented player who can play with his right foot and also with his left," he told Eleven Sports after Pietuszewski's first appearance of this season, a late cameo in the 3-1 win over Benfica in September.
"He is fast and works hard for the team."
Pepe also had a warning.
"He is not a normal young man who, at his age, can go to the bar or the nightclub," he said. "After training, he has to stay home and rest, so he is ready for the next day."
Not everyone around him is that sure of the timeline. Siemieniec told a Weszło podcast in October 2025 that Pietuszewski could still be a liability as well as a match-winner.
"Oskar is a player with a mentality where he can come on and win a match, but he can also come on and spoil it," he said. "I still see a lack of consistency in him, in terms of readiness in every game."
Francesco Farioli has had to manage that edge at Porto. After Pietuszewski was substituted in a 3-1 win at Estoril in April and reacted angrily on the bench, the coach waited until the players had showered and his press conference was over, then spoke to him calmly and pointed to the club crest. Fellow Pole Jan Bednarek had already warned him that a second yellow card was only a reaction away.
Muscle trouble then cost him the start of the season. He returned in October to score the winner at Marítimo, though Farioli was candid about the state he was in.
"Oskar came back in a worse condition than the one he was in," he said. "He told me he could last 15 or 20 minutes."
Pietuszewski made his Poland debut as a half-time substitute in the 2-1 playoff semi-final win over Albania on 26 March and has six caps. National team coach Jan Urban had forecast it after the Benfica goal.
"I am sure that, playing like this, sooner or later he will undoubtedly get into the national team," Urban told Antena 1. "He has enormous talent."
Urban's one condition was simple.
"He has to know how to take chances. But from what I've seen, Oskar has his head screwed on."
For now, Pietuszewski is a Porto player whose coaches agree on his ceiling and disagree only on how quickly he reaches it. Farioli wants him to put the team first; the next test is whether he can stay on the pitch for longer than 20 minutes.