Cesc Fábregas has told Manchester City, who Arsenal face on Sunday, that they may be able to afford the best players but their riches cannot buy them instant team spirit.

The Arsenal captain believes it is the key element Roberto Mancini will struggle to create despite being able to reach into the coffers of City's owner, Sheikh Mansour. "Of course you cannot buy it in one year," said the Spaniard, who returned from a hamstring injury in the Champions League game against Shakhtar Donetsk last night, scoring the third in a 5-1 win.

"You need a few years to get everyone together to know everyone well, all the players. It's not easy. You don't do it in one season or two, I would say. Of course they are in a very good position – they have all the ingredients to become a great club. We have to fight hard against them."

City are second in the league, three points ahead of Arsène Wenger's team going into the meeting at Eastlands. Wenger's ethos has been to buy modestly, and nurture homegrown talent but Fábregas was reluctant to criticise Mancini's lavish summer spending, which has included Mario Balotelli (£24m), James Milner (£26m) and Yaya Touré (£24m). "Everyone chooses their own politics, everyone decides how to win," he said. "They have a lot of money, they are taking advantage of it and that's it. It's not our style, but we respect everyone's decision."

City represent the latest test of Arsenal's ability to win the league, six years after the Invincibles went unbeaten to claim their last championship. "They are improving, they have a lot of money, they are buying good players so you expect them to be at the top level," Fábregas said. "It has always been difficult since I've been here to go to Manchester City. I remember my first few years – it was difficult but now they have some of the very best players in England."

Three weeks ago Chelsea defeated Arsenal 2-0 at Stamford Bridge. Tomas Rosicky, who operated on the right against Shahktar, is clear that City must now be beaten to indicate Arsenal are serious challengers. "It's a massive game. We couldn't wish for a better result before this game and we want to do better than against Chelsea," he said. "I think this team will show it. It was the same old story [against Chelsea]. How we presented ourselves there, we were very disappointed.

"But you ask whether we will go out from this game [against Donetsk] with the feeling we can do it: all this stuff, is just words. We need to finally show it on the pitch. We cannot always say we are unlucky, it doesn't work like that. It's time to prove it."

Rosicky said that while Wenger has not formally talked about the requirement to have a ruthless mentality, everyone at the club is conscious of it. "I wouldn't say we are discussing it, or we had meetings about it. But I think everybody has realised how it is and I know that I will say it again but we finally need to show it on the pitch. We have a great opportunity to show it on Sunday and this [result] was a good boost before the game."