As September drew to a close a year ago, Arsenal were just about getting their breath back. The start of the season had hit them in the manner of the cat getting it Tom and Jerry style – they were metaphorically sucked up by a vacuum cleaner, which exploded to propel them into the fireplace, which they leapt out of to be whacked by a bulldozer. In the middle of this maelstrom, a man with perfect hair, a flawless smile and a polished, precise footballing style arrived to help. Ever since he walked in the door at the Emirates, a rushed deadline day signing, Mikel Arteta has been a picture of composure.

The Spaniard joined Arsenal at a time when their midfield was in bits. Arsène Wenger had recently lost three key components from the previous season; Cesc Fábregas and Samir Nasri left for Barcelona and Manchester City, while Jack Wilshere was grappling with the injury problems that would deprive him of the entire season and then some.

Arteta's switched-on football sense was something that Arsenal were able to lean on immediately. Over the course of an excellent first season, he reinvented himself as a deep-lying midfielder, who relies as much on his awareness – the ability to spot danger and spy openings – as his technique to deal with all those situations. He has become an indispensable member of the current squad. Wenger is enthralled by the way he has established himself in a new position, compared to the days he foraged in more creative role on the flank for Everton. "I am hugely impressed by him," says the Arsenal manager. "I am impressed by Arteta because he is a tactical leader and a winner."

There will be no authentic defensive midfielders during this weekend's capital showdown between Arsenal and Chelsea. Not a single one. Nothing resembling a Patrick Vieira or Claude Makélélé. Nobody acting the part of Gilberto Silva or Michael Essien. There will be no powerhouse, no natural ball-winner, nobody inclined to just sit and hold.

Arteta will be assisted by Abou Diaby, who Wenger has in the past favoured in the No10 position. In opposition, Roberto di Matteo tends to use a midfield platform of Frank Lampard, whose play in and around the opposition penalty area is the stuff of club legend, and Mikel John Obi, who grew up playing a more attacking style before his size and strength convinced managers to try to mould him into more of a shielding role.

"There are no defensive midfield players at the moment," explains Wenger. "We try to find the defensive balance collectively. We have less players who are purely defenders but you can be physically strong in defending like Diaby, tactically strong like Arteta. At the moment we have the balance because everybody participates, but we have less specialists, purely defenders. We are more versatile going forward because everyone has the potential to go forward."

It is an interesting – if risky – development. Arsenal were expected to sign one of those specialists over the summer, especially when Alex Song was sold to Barcelona, but Wenger was struck by this idea of trying to evolve his team to function better without one. As it turns out, Arsenal's midfield has so far played with intuitive balance, with the foundation built by Arteta and Diaby providing Santi Cazorla – "a very exciting player to watch, he's been a highlight so far," says Di Matteo – with the freedom to express his shimmering talent. As a midfield trio, the blend has been very encouraging so far. Wilshere's anticipated return to the mix adds another string to the midfield bow.

Wenger is mindful that his decision to abstain from using a proper defensive midfielder is like hovering over a fine line – the promise of a variety of starting points to launch attacks is on one side, the threat of not enough protection on the other. "That is what is at stake against Chelsea," Wenger says. "Will you be strong enough defensively, in midfield as well, to deal with them? That's where one of the tests will be."

Chelsea have their own examination ahead. While their position at the top of the early table, unbeaten, is not to be sniffed at, they have at times this season looked like a team trying to adjust to a new ideal. The midfield base of Lampard and Mikel has not been entirely convincing.

"Frank in a 4-2-3-1 has been playing a bit deeper, but he still manages to get into the box at times," explains Di Matteo. "Maybe with less frequency, but we don't want to take away his ability to arrive into the box with the right timing. Hopefully the new players will add some goals and assists to our team."

Locating a new rhythm in an attack without Didier Drogba leading the charge, with three agile playmakers flitting behind Fernando Torres, is still a work in progress. Wenger is curious to see how it pans out, with Chelsea gaining delicacy but losing force as they bed in their new style and new players, among them Eden Hazard and Oscar. "A generation have arrived slowly at the end and they were in a position to bring in some young players and they wanted to change their style a little bit – that's obvious in their choice of players. But as well when you think about Chelsea, they had physically, contact wise, a very impressive side with Drogba on top of that. Maybe there are not the same players available now on the market."

Can they be as potent without Drogba? "We will have to give you the answer on Saturday afternoon. We face Torres who on his day can be a handful as well. He looks to have found the form again and is very mobile now and has found confidence back. It's a different style."

Wenger was surprised that Chelsea finished outside the top four last season, even though they understandably focused on the cup competitions. Their Champions League triumph is, he believes, something to savour, rather than feel a pang of envy about. "I am proud that the Premier League teams win it. What would worry me is that we have no chance in the Premier League," Wenger reckons. "You can say to people that the team who finished sixth in the league can win the European Cup. It's absolutely fantastic for the Premier League."

Di Matteo insists Wenger has the squad to challenge for the title this season. "I said at the start of the season they would be challenging for the league. I haven't changed my mind. They have signed some very good, interesting players. They have been playing the same kind of football for many years. Personnel has changed, but the philosophy hasn't."