Back when Arsenal's strength of character was being questioned in the wake of late capitulation at Newcastle, a list of natural born leaders had tripped off Theo Walcott's tongue with only one name raising eyebrows. To cite Cesc Fábregas or Robin van Persie, senior internationals in a youthful team, seemed obvious. Gaël Clichy too, as the last remaining member of the Invincibles. "And there is Johan Djourou, a great leader as well," said Walcott. It was delivered as an assumption, almost a gimme, yet the mention meant so much more.

Other members of Arsène Wenger's side have drawn the focus this season, whether it has been the resurgence of Samir Nasri or the emergence of Jack Wilshere that has caught the breath, but the Swiss centre-half has arguably felt more like this team's find of the campaign to date. Djourou has been transformed from an injury-prone bit-part player, all promise and no product, into a key member of the backline. Barcelona boast the capacity to provoke panic on Wednesday night, but the 24-year-old at the heart of Arsenal's defence will exude calm authority as the visitors, all a blur, tear at him.

The Ivorian-born defender has waited patiently for this opportunity to prove his class. So much of his career has been lost to injury, with last season virtually a write-off after serious knee ligament damage restricted him to a solitary appearance as a substitute on the final day. Yet, with Thomas Vermaelen now the one suffering on the sidelines, Arsenal have increasingly learned to lean on the man plucked from Etoile Carouge FC in Geneva as a teenager. Fábregas summed up his importance: "With the way we play, we have needed a centre-back like him: strong, good on the ball, quick, making his presence felt on the opposition's strikers." Arsenal may have stumbled upon the answer.

Whether this team can prevail against Barça's mesmerising talent over two legs remains to be seen, but they will clearly require strength and pace at the back along with a willingness to hassle and harry all over the field if they are to stand any chance. Djourou offers presence and power, as well as aggression. There was an admission this season that a year on the sidelines had changed his attitude. "Maybe I was too nice," he said. "I was a boy before the injury, looking up to the guys in front of me, but now I'm a man. The injury gives you a lot to think about. It made me angry because I wanted to be playing."

He has his chance now. Even with his knee problems, he remains the quickest of Arsenal's centre-halves and, at 6ft 4in, he is more imposing than either Laurent Koscielny or Sébastien Squillaci at his side. That diminutive combination has been employed 14 times this season with the team shipping 22 goals in those fixtures. Djourou, in contrast, has not finished on the losing side in the Premier League since a 3-0 loss at Manchester City in November 2008, with the team breached just 14 times in his 25 games this term while he has been on the pitch. His selection prompts confidence these days.

His absence has the opposite effect. Wenger's decision to omit him for the derby against Tottenham Hotspur at the Emirates in November, a contest lost 3-2, felt more significant in hindsight. Newcastle rallied after his withdrawal at St James' Park – he departed injured a minute before Abou Diaby's dismissal – and it is a measure of Djourou's progress that it feels inconceivable that the visitors would have caved in so spectacularly had he remained on the pitch.

It is the sense that Arsenal now boast a partnership at the back which reassures most of all. Djourou's chemistry and understanding with Koscielny in recent weeks, established most notably perhaps in the 3-1 victory over Chelsea and their dominance of Didier Drogba that night in December, has helped the Frenchman overcome an awkward start to his career in England since his £9.7m summer move from Lorient. Djourou is a commanding presence at Koscielny's side. When Vermaelen returns from achilles trouble and is integrated back into the first team, it feels unlikely now that the Swiss will be the one to make way.

Djourou would expect as much. He is, after all, an international with 25 caps. Yet he began this season feeling like a fourth choice at the Emirates Stadium and has since come of age. Wenger has treated him cautiously, his initial fears that Djourou could not play three times a week gradually easing as the centre-half's progress has been maintained. "He has gone from strength to strength since the start of the season," said the manager. "When the team have had difficult moments – when we have had to defend in the air – he has been dominant. And he has not only shown dominance but personality as well."

That will be needed aplenty against Barça, when Arsenal must push and press high up the pitch to stifle the visitors' attempts to monopolise possession. The hosts' centre-halves are sure to be overworked regardless but, at last, this team do not feel rendered vulnerable by a soft underbelly. Djourou has a point to prove.