It was another breathless encounter and, this time, Chelsea will not care too much about the refereeing they think went in Manchester United's favour. They were behind three times, dragged the game into extra time with a 94th-minute penalty and, finally, booked their place in the quarter-finals by the odd goal in nine.

Where to start? This was also a night when the referee, Lee Mason, booked nine different players and was fortunate, perhaps, that Eden Hazard's penalty spared him another inquest about a key decision going against Chelsea. Mason had missed a pretty obvious penalty not long before when Juan Mata's cross struck Michael Keane, United's 19-year-old centre-half, on both arms.

In the end it was largely inconsequential, thank goodness, and Sir Alex Ferguson's decision to play two raw and inexperienced centre-halves eventually counted against his team. Scott Wootton, 21, was culpable for giving away the penalty Hazard converted when he bundled over Ramires. The same player then gave Sturridge the chance to put Chelsea ahead for the first time when he failed to get enough on his header back to the goalkeeper, Anders Lindegaard, seven minutes into the first period of extra time. Wootton and Keane tired badly during the late stages and the younger man was fortunate not to be sent off after fouling Sturridge when he was the last defender.

Chelsea, on the balance of play, deserved to go through. They, like United, were guilty of some terrible defending at times, but they had subjected their opponents to some draining second-half pressure after Nani made it 3-2 just before the hour. It was difficult thereafter to keep count of the number of chances they accumulated before the late flurry of goals that culminated with Ramires eventually putting in Chelsea's fifth, going round Lindegaard after some lovely play from Hazard. Even then, there was another late twist at the other end as César Azpilicueta fouled Javier Hernández to give away the third penalty of the match. Ryan Giggs completed the scoring on a night of drama, excitement and intrigue, but very little in terms of organised defending.

The tone had been set in the 22nd minute when Petr Cech played a short goal kick to Oriol Romeu and the Spaniard dithered, lost the ball and watched helplessly as Giggs picked his spot to open the scoring.

David Luíz's penalty, after Alex Büttner's badly-judged trip on Victor Moses, made it 1-1 nine minutes later but the Chelsea defender then reminded us of his own capacity for inviting trouble, running over the halfway line with the ball and being caught in possession. The Luíz slalom undoubtedly looks good when it comes off, but it also has a habit of endangering his team when he loses possession. Rafael won the ball, Anderson played the killer pass and Hernández did the rest with an angled shot.

So much has been written about what happened when these sides met on Sunday and, specifically, whatever Mark Clattenburg reputedly said to Mikel John Obi and Mata, it seems to have been almost overlooked that the two sides both came away from that match with considerable questions about their defending. In truth, their reconfigured line-ups – Sir Alex Ferguson made 10 changes to his United team, and Di Matteo settled on six – fared even worse. The night was rife with carelessness.

Chelsea, though, played with the greater urgency in the second half and had the stronger, more experienced bench. Ramires and Hazard were among the substitutes and their introductions had a significant impact.

Sturridge had passed up two presentable opportunities by the time Mata, Chelsea's best player, swung a corner over from the left and Gary Cahill issued another reminder about what a handy knack it is when a centre-half can cause problems in the opposition penalty area. His header had flashed past Lindegaard and gone a yard behind the goal-line by the time Rafael turned it against the crossbar and out.

This was the first spell of the match when Chelsea were clearly on top but they were level for only seven minutes, Nani scoring with a lovely, clipped finish, bursting into the penalty area and dinking his shot over Cech at the end of a cultured exchange of passes involving Hernández and Anderson.

What followed was an extraordinary succession of near-misses, desperate clearances and wasted chances in front of Lindegaard's goal. United always carried menace in their own attacks but they were in a dishevelled state by the end. Ferguson withdrew Büttner after a difficult first half for the Dutchman, moving Rafael to left-back and Darren Fletcher to the right of defence. In the circumstances, it was probably no surprise they were so vulnerable.

For Chelsea, reflecting on a trip to Leeds United in the last eight, it will not make up for what happened on Sunday, when their unbeaten record in the league was sacrificed. Yet it still represents a satisfying evening's work, particularly given how close they were to going out.