Basking in the glow of the masterpiece match-winner that was the talk of Europe this week, Mesut Özil made his way serenely, contentedly, back towards London. It seemed as if half of Bulgaria wanted a bit of him before he left. He gladly had time for everyone – finessing every photo, every signature, every word of appreciation with a special touch.

It was not so long ago this particular player’s body language was routinely picked apart. He was too languid. Too casual. Did not want to know. Wilted under pressure. All softness without the required substance. Too many big games passed him by ... but those criticisms have faded into the shadow of an emboldened talent who is relishing the spotlight.

The Özil of today carries himself differently. The composure and confidence represents how he is enjoying the feeling of being centre stage. That is what is expected of him on Sunday, in the heat of the north London derby, where the early title credentials of both teams will undergo a particularly spicy examination. Tottenham have ruffled Arsenal at the Emirates in the last couple of seasons, requiring late equalisers from the home team to save face. It promises to be as frenetic and fierce as usual, which is not the stereotypical idea of Özil’s favourite environment.

Yet there is more obvious determination in him to want to influence games these days. “He pushes himself much more,” Arsène Wenger says. For a start he is much more muscular than the slender figure who arrived at Arsenal, discarded by Real Madrid, three years ago. It has been known for defenders to bounce off him this season, a far cry from the elegiac shrug he used to give when unsettled by some opposing hulk.

His reinvention as a player who has added a striker’s runs to his playmaking passes looks intriguingly transformative. Özil the goalscorer? Who would have thought it? Well, Wenger did. It took some time, and some encouragement but Özil’s adjusted position, as a high 10 rather than a deep-lying creator, makes him an even more effective performer.

“I convinced him that he has it in his locker to score goals,” Wenger says. “He was more focused on giving and looking. Today he understands he can have those qualities but as well be on the end of things. The timing of his runs is good. In training I noticed he is a very good finisher. When you have that in your locker you have to try to get it out. Slowly, he now realises that. Now he makes more runs to score goals. On top of that he has a fantastic attribute of a guy who is a good finisher – he is calm. You notice all the finishers are killers. That means they keep their nerve in front of goal and he has that.”

The old Dennis Bergkamp comparison has been aired recently. Wenger sees the similarities and is urging his current master of technique to do what it takes to earn the kind of status Bergkamp enjoyed at Arsenal. “He can be a legend if he commits,” Wenger says. “Dennis Bergkamp committed for a long period, he played until he was 38. I wish we have 10 more years of Özil. To become a legend at the club you need to stay for a long time. If you stay two years you would not be a legend.”

Arsenal are doing their best on the contract front to secure an extension. “We work on it,” Wenger said, accentuating the positive sign of how content Özil seems on and off the pitch. “A player needs to meet his needs inside a club. It is difficult not to be happy in London and happiness that a player has when he plays comes out by his performance.”

It is typical of how Özil has come out of his shell that he is keen to be a face of the club more readily. In this weekend’s buildup, he took part in a social media Q&A session. The hashtag #AssistMeMesut invited fans who needed some help with anything to ask Arsenal’s No11. Some of the requests were unsurprisingly left-field. Özil filmed answers to a handful of questions, ranging from a Turkish restaurant recommendation to relationship advice. “So my friend,” Özil told @theDjole, “Just be nice to her, show her your qualities and I wish you all the best.”

Wenger remembers the day well when Özil arrived in a flurry of deadline day activity in September 2013. “In fact on the day we signed him we played against Spurs,” he says, breaking into a grin. “We won without him.” It was a landmark signing for the club, at £42m demolishing its transfer record.

Özil has grown into life at Arsenal. Even for a player with his experience and the expectation that comes with such a high-impact signing, it was a slow burn. The efforts that have been a hallmark this season took some time to develop. Wenger acknowledges the Premier League was a bit of a culture shock for Özil. “He left some people sceptical – saying he didn’t go too much into challenges or tough contact. [He punches his hand for emphasis.] He’s a player who is more a guy whose strength is to get out of things but on the physical front I believe he’s improved as well.”

For Wenger, the main difference between the Özil he signed and the one he will pick this weekend boils down to commitment. “He is 28, an age where he is more mature. The difference today is he focuses more on efficiency. When he arrived here he was more focused on playing. Today efficiency is more in his mind. Sometimes the trap for very talented players is it is easy for them. They know subconsciously they don’t need to push themselves too hard to be efficient. It’s so easy.”

The desire to push himself more is making a tangible difference to his game. Özil’s increased runs, added to the indefatigable darts of Alexis Sánchez, make it that much more difficult for defenders to guard their area. Arsenal are less predictable and more punchy.

Tottenham arrive at the Emirates as the league’s dominant rearguard, with only five goals conceded, so Arsenal will need their front players to continue their lively form. Sánchez has scored eight, and Özil seven (Theo Walcott, who is hoping to return to fitness, also has eight and Olivier Giroud is trying to catch up), so Arsenal feel they have goals in them even against a resolute opponent.

So has Özil changed enough to become the type of player determined to take a tough derby by the scruff of the neck? He excelled recently in the 3-0 defeat of Chelsea, and he will be expected to emulate that performance against Tottenham. “That’s what you want,” Wenger says. “Of course he can be dangerous but in big games there is always a lot of expectation from him. But I believe that depends more on the team performance. If the team performance is strong then Özil will always shine.”