After going through the whole of 2011 without losing on their own ground, Manchester City have now been beaten twice in the space of four days and are beginning to look conspicuously thin around the edges. Steven Gerrard's 13th-minute penalty puts Liverpool in a position of strength going into the second leg of this Carling Cup semi-final and it will need a significant improvement from the Premier League leaders to prevent Kenny Dalglish's team confirming a date at Wembley.
The two sides renew acquaintances at Anfield in a fortnight and Liverpool, the seven-time winners, should be greatly encouraged about the way they matched and, at times, outdid a side that have managed 56 league goals compared to their own tally of 24. Dalglish's men deserved their lead, threatened more goals and then eventually settled for a backs-to-the-wall operation during a second half in which the home side's possession was not accompanied by the wit or gumption to break down their opponents.
Liverpool's great strength so far this season has been their defence and here we saw all those qualities of industry and organisation.
City looked laboured, playing with little of their usual fluency and, though Glen Johnson's studs-up challenge on Joleon Lescott dominated a lot of Roberto Mancini's post-match analysis, the truth is it was a sideshow to the real story of a team who were always a good notch or two below their usual level.
This was City's fourth defeat in eight games and the first time they have not scored at home in 14 months. Mancini had warned this kind of performance might come as they waded through a hectic fixture schedule deprived of key players. A lot of energy and emotion was spent in Sunday's FA Cup defeat to Manchester United and they badly missed their captain, Vincent Kompany, as well as two of their other mandatory first-team picks, David Silva and Yaya Touré.
Liverpool, in contrast, began the game as if affronted by the memories of their 3-0 league defeat here last week. They were quick to the ball, strong in the challenge and, once they had established the lead, they played with know-how and composure. If Johnson's challenge risked a red card, it should not be overlooked that this was in stoppage time and, as such, would almost certainly not have affected the result.
Mancini's anger stemmed largely from what he perceives as double standards at a time when Kompany was watching from the stand after his own red card against United, a decision the City manager maintains is the worst he has seen in 30 years in football.
Perhaps in hindsight he might regret not moving Micah Richards across from the right side of defence to partner Lescott in the centre and bring in Pablo Zabaleta at full-back. Instead, Stefan Savic was given the responsibility of replacing Kompany and, though Richards was excellent as an overlapping right-back, overall it was a gamble that backfired.
Savic gave away the penalty with a challenge on Daniel Agger that was raw and mistimed, catching him just above the knee, and it was not his only mistake of a difficult evening.
Even before then, there were three separate moments when Liverpool were kept out only by Joe Hart's goalkeeping. The pick of those saves, diving full length to turn away a deflected Stewart Downing volley, was truly exceptional. It was rare, however, to see City so vulnerable and it was in this flurry of Liverpool attacking that eventually led to Savic's inexperience showing and Gerrard driving his penalty into the bottom corner.
Liverpool lost Jay Spearing to a tight hamstring in the first half but their momentum was not badly disrupted. Charlie Adam came into a midfield in which Steven Gerrard and Jordan Henderson were excellent. They restricted their hosts to only one clear chance in the first half, when James Milner turned Richards's cross over the crossbar. There were some anxious moments for Dalglish's men after the break, when Mancini experimented with a three-man defence, but Pepe Reina was excellent in the few moments when he was exposed, blocking a leaping header from Richards and doing enough to put off Sergio Agüero after the Argentinian had intercepted Martin Kelly's backpass.
As for Mario Balotelli, the striker lasted only 39 minutes before being withdrawn. Shortly before, he had allowed a simple pass to run over his foot and go for a throw-in. Mancini said his player was still struggling with an ankle injury but it was tempting to wonder if there was more to it and there was something very deliberate about the way the two men ignored each other on the touchline.
City huffed and puffed but the late onslaught that might have been expected never really materialised. Liverpool held out fairly comfortably, and will almost certainly reach the final unless City can rediscover some of the old stardust.