After clean sheets against Leicester, Everton and Crystal Palace, it seemed Manchester City had found a formula for defending without their injured inspirational skipper Vincent Kompany.
However, against West Ham, Manuel Pellegrini's defence - marshalled by centre-backs Nicolas Otamendi and Martin Demichelis - struggled badly.
West Ham took the lead less than a minute after kick-off and, in the second half, scored another through a quickly-taken Michail Antonio long throw.
Jamie Redknapp and Stuart Pearce analysed Manchester City's defensive errors in the Sky Sports studio and, aside from the goals, they had plenty of other examples to work with.
"You're not talking about young players at the back," said Redknapp. "They're all international players and they should be doing better.
"Whether Vincent Kompany is playing or not, it shouldn't make that much difference. But unfortunately, they seem unable to cope when he doesn't play."
The difference in City's defensive record with and without their captain is stark. They have conceded just two times in his nine appearances this season. They've shipped 21 goals in the 14 games without him.
That is translated into a significant difference in terms of the average number of points they've won per game with and without Kompany and Pearce believes City are badly missing his leadership.
"The long-throw goal is symptomatic of why Kompany is so important," explained the former England and City defender. "You can't concede from a long throw like that, let someone run straight behind your defence from 40 yards and put the ball in the back of the net.
"It's leadership. That's what Kompany brings, not only what he gives you as a player. It's that little bit of leadership, pulling people around, getting them on their toes and getting them focused."
However, it seems City will have to deal without their captain for a little while longer yet. Kompany is continuing his recovery from a persistent calf problem and Pellegrini says his return is still weeks away.
"Vincent has at least two or three weeks more so he's not able to work with the squad," the City boss told Sky Sports. "When he starts working with the whole squad then he needs at least one week more to return."
If Kompany is to miss the next three weekends, he'll be absent for City's Capital One Cup semi-final second leg at home to Everton, their FA Cup away day at Aston Villa, plus their Premier League trip to Sunderland and home league fixtures with title rivals Leicester and Tottenham.
If City are to maintain their challenge across three different domestic competitions, they will need to find a way to improve on their defensive performance at West Ham, without Kompany's help.