Chelsea's cavalier style suits Mata but leaves Wenger with a headache London's two most successful sides of recent years will make the customary transition to Champions League games this week in different mood. Each will be expected to win, but in Arsenal's case at home to Olympiakos a tightening up at both ends of the pitch will be required to offset the bitter disappointment of Saturday's 2-1 defeat, whereas Chelsea merely need more of the same against the Danish champions Nordsjælland. Arsène Wenger was understandably upset that his team were "passive on both goals" conceded and Laurent Koscielny, at fault twice, is likely to pay the price by making way for Per Mertesacker on Wednesday. The other important Arsenal fixture this week is an Under-21 game against West Bromwich Albion today in which Jack Wilshere (after 14 months) and Emmanuel Frimpong will return in midfield. As for the European champions, Roberto di Matteo has been charged with simultaneously improving both results and style in order to keep his job. So far, so good on both counts with a three-point lead at the top of the Premier League and acclamation too for artistic interpretation as £57m worth of new recruits in Eden Hazard and Oscar join up with Juan Mata in a midfield trio that might have seemed to be too much of a good thing. Against Stoke City's roundheads the previous week that was the case but Arsenal's more similar style enabled the three cavaliers to prosper. "They're intelligent players and we're trying to integrate them into our system," Di Matteo said, while warning: "They have to realise they have responsibilities too. They have some freedom but still we need to keep some kind of discipline when we're out of possession. I still think we have to improve a lot on that side. As exciting as it is to have them all on the pitch, when we lose the ball we need to be able to defend as well. All three would rather play in the centre immediately behind Fernando Torres, but Mata learned last season about coming inside from a wider starting position and Hazard is slowly doing the same. Spaniard Mata, whose free-kicks led to both goals on Saturday, is also benefiting from extra time after taking part in the European Championship and then the Olympics, as well as sitting out a couple of recent games. "I like to play with the ball, try and assist, with passing, with movement, with freedom and I think it's what Eden, Oscar and me are doing at the moment," he said. It may be that one of the trio sits out tomorrow's game in Copenhagen, when Frank Lampard will be desperate to return after being left out of the last two League matches. At 34, his future will be much discussed unless or until a new contract is signed in the next few months. On Saturday, Di Matteo left him stewing in the dug-out all game, sending on much younger men in Victor Moses and Ryan Bertrand as Chelsea played counter-attack in the last half-hour after Mata had restored their lead. John Terry, as imperturbable as ever, held the defence together, although Petr Cech was required to make two fine saves and Olivier Giroud and Santi Cazorla missed good chances. Yesterday the former Football Association chairman Lord Triesman said black players would feel let down by the Terry case and that he should not have continued to play for England until it was heard - although that should have been much sooner and without waiting for Terry's court case. "As you talk to black players, what you will find is they respect him as a player but they really feel let down," he said. Olympiakos still perfect David Fuster ensured Arsenal's Champions League opponents Olympiakos continued their 100 per cent start to the league season with a 1-0 win away at Atromitos. The Spaniard headed in from a Jose Holebas free-kick to send Leonardo Jardim's men three points clear at the top. Meanwhile, Nordsjaelland swept Danish Super Liga strugglers Esjberg aside 3-0 on Friday to keep them on the coat-tails of league leaders Copenhagen. Joshua John, Kasper Lorentzen and Nicolai Stokholm were all on target for Chelsea's opponents. Goals: Arsenal Gervinho 42. Chelsea Torres 20, Mata 53. Subs: Ar Oxlade-Chamberlain 7 (Diaby, 17), Giroud 6 (Podolski, 67), Walcott 6 (Ramsey, 67). Ch Moses (Oscar, 73), Cahill (Luiz, 81), Bertrand (Mata, 85). Booked: Ar Ramsey, Vermaelen. Ch Oscar, Luiz, Ramires. Man of match Hazard. Match rating 8/10. Poss: Ars 51%. Chels 49%. Attempts on target Ars 4. Chels 3. Ref M Atkinson (Yorkshire).