Manchester City, once again, left their fans craving more. This was another performance to frustrate their supporters – the most expensively assembled team in English football lacking the wit to break down an obdurate Birmingham side – and the crowd's dissatisfaction manifested itself in the first show of open hostility against manager Roberto Mancini in his 11 months in the job.

The dissent was loud and prolonged, even vicious at times. Mancini's decision to replace a striker, Carlos Tevez, with a defensive midfielder, Gareth Barry, five minutes from the end was particularly contentious, prompting an enraged chant of "What the fuck is going on?" The song in support of Craig Bellamy, loaned to Cardiff City after falling out with Mancini, told another story, as did the boos at the final whistle and the angry shouts directed towards the Italian around the dugout.

To give them their due, Mancini's team subjected their opponents to concerted pressure in the second half, but it was still a flat and uninspiring performance, and the lack of penetration was alarming considering the immense amount of money that has gone into this team. The closest they came to a goal was when Steve Carr cleared James Milner's shot off the line a minute into the second half, but, that apart, this was a performance that compounded the growing suspicion English football's richest spenders are not playing with the adventure expected of a club that began the season promising a serious tilt at the championship.

"I'm as frustrated as anyone," an animated Mancini said afterwards. "I wanted to win, I didn't want a draw. We had 17 chances in the second half. OK, the first half we played slowly, but the players are not robots – they have been playing every three days and they are tired."

Explaining the withdrawal of Tevez, he added: "Carlos has had a little injury for two to three weeks and I thought it would help us create chances by putting on Barry. We have had a problem all season and it is that if Carlos does not score we haven't another player who can score a goal."

This was an unusually pugnacious Mancini and he reacted indignantly when he was asked whether he felt under pressure. "What pressure? You say I'm under pressure – I'm not under pressure. We are fourth; we have some problems and we must improve, but what pressure? Because the supporters say: 'Oh, we should put on two strikers'? If you want us to entertain I could put on three strikers. Do you think that would help? Or do you think the side would lose balance?

"All supporters think like this, in England and Italy. But if they think that I should put on four strikers and we would score four goals ... no, that's not the way football is. If football was like that, I would put on 10 strikers." Whether that argument will appease the supporters is a matter for debate.

The criticisms of Mancini being too negative accelerated after the 0-0 draw with Manchester United last Wednesday, but at least on that occasion they were confronted by a side challenging for the Premier League. Birmingham have not won away from home since March and had fallen to 17th in the table going into this match, a point off the relegation places.

Tevez was aggrieved five minutes before the break when he turned the ball past Ben Foster only for the referee, Mike Jones, to rule he had used his arm, which brought the Argentinian a yellow card in the process. Birmingham, however, had their own complaints in the first half and their manager, Alex McLeish, argued that his side should have been awarded a penalty when Liam Ridgewell went to ground, claiming Adam Johnson had clipped his heels.

Johnson, the subject of criticisms from Mancini over perceived behavioural flaws, foraged without success and it was noticeable, too, that Milner ran straight down the tunnel when he was substituted.

Another memory that will linger was keeper Joe Hart's frustration, more than once, when he looked to take a quick throw and found no team-mates showing for the ball.

There was audible dissent shortly before the interval when Jérôme Boateng played a pass back to Vincent Kompany rather than going forward and, although McLeish described the second half as "a bit scary", the volume was turned up another notch against the home side at the final whistle.

THE FANS' PLAYER RATINGS AND VERDICT

ROBERT O'BRIEN, Observer reader They played well but we were really bad. We found it easy enough to get into their box but we've become too predictable, and opponents are well aware of Carlos Tevez's threat now. And in the background we've got a battle of wills between the players and Roberto Mancini that resulted in him subbing Tevez just to make the point that he's the boss. It's important that Mancini wins that battle. Birmingham defended well and thwarted us but never looked like scoring. It's hard to tell if the players are lethargic or are being told to play like that. James Milner still hasn't had a decent game for us since his arrival.

The fan's player ratings Hart 6; Boateng 6, K Touré 6, Kompany 6, Kolarov 6 (Zabaleta 81 5); De Jong 7, Y Touré 5; A Johnson 5, Silva 7, Milner 7 (Santa Cruz 66 5); Tevez 6 (Barry 83 6)

JOHN PRICE, Observer reader An away point at City will do us nicely. The highlight of the day was probably hearing their brilliantly short-memoried fans winding themselves up and booing Mancini for being negative. But that still shouldn't overshadow some great performances in our side: defensively we totally stifled anything they had, Lee Bowyer was as good as he's ever been for us, and Stephen Carr and Ben Foster stood out too. Zigic wasn't brilliant – he's lacking mobility, but I still think he'll develop into a great asset for us. But maybe the most encouraging thing was the team spirit: we never stopped running.

The fan's player ratings Foster 9; Carr 9, Johnson 8, Dann 8, Ridgewell 8; Larsson 7, Ferguson 7, Fahey 9; Gardner 7 (Bowyer 49 9); Zigic 6 (Hleb 65 6) Jerome 8,

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