When Chelsea were beaten 4-2 at home by the newly enriched Manchester City in the spring of 2010, it proved only a glancing blow rather than a fatal wound to their title aspirations.
Carlo Ancelotti's side, as they then were, still managed to win the more critical game away to Manchester United and win the League. But they must have feared that the crowing of the visiting supporters that day would be repeated in years to come as the Abu Dhabi millions kicked in.
Last season Chelsea managed to win the home game 2-0 with two late goals but only finished above City by virtue of having scored more. The chances of any team outscoring them over 38 games this time already seem remote and they come to London tomorrow night 10 points ahead of the team that Andre Villas-Boas is slowly reshaping.
Villas-Boas's daunting task has been to keep them in contention for trophies at the same time as improving the entertainment levels and reducing the average age.
The latter process is taking shape at least; compare the ages of four of last season's regulars in Alex (29), Frank Lampard (33), Nicolas Anelka (32) and Florent Malouda (31) with their replacements for their recent games: David Luiz (24), Ramires (24), Daniel Sturridge (21) and Juan Mata (23) – a decrease of 33 years.
Of course, there is still room for experience, especially down the spine of the team. Whether or not it was the intention to encourager les autres by substituting Lampard after an hour at Newcastle, then leaving him out for a third straight 3-0 win, against Valencia last Tuesday, Didier Drogba (33), John Terry (31) and Petr Cech (29) were all outstanding. Villas-Boas is now pondering whether to back Drogba's demand for a new two-year contract, while insisting that Cech will not be sold.
The goalkeeper, from his vantage point behind the rest, has a unique view of how the side are performing and in his opinion the recent improvement in results was always on the cards once scoring chances were no longer frittered away.
"We created so many chances we didn't convert, and basically every mistake we made we conceded goals," he said. "Now we've got three clean sheets in a row, scored goals and killed the games off.
"Against Valencia not everything was perfect again and we know that. But in a difficult moment you need to go step by step. We could see Didier at his best, absolutely brilliant, gave everything for the team and scored important goals. That's the player we always knew. He's been one of the best strikers in the world for all his career and you can see he still has that quality."
It was a very different Chelsea on Tuesday, scoring early then filing back into defence with diligence and organisation but not in a manner to excite the home fans. Cech does not believe that will be the approach tomorrow, if only because City hold a considerably greater threat than Valencia going forward and are, he says, vulnerable at the back
"Their main strength is their midfield and their attack because they still concede chances. Joe Hart has been having a very good season, that's a main reason they're winning games. But they do concede chances at the back so defending is not their strongest point. So far they've been converting chances and took advantage of that, but who knows if they can keep scoring like that?"
Or, indeed, keep winning. But can Chelsea realistically close a gap of 10 points? "We still can because there are so many games to be played. We all remember last season when we were so many points ahead of Man United, then so many behind them, and in the end we played a game at Old Trafford, we played for everything and we could have won the title but it went the wrong way and we finished only second.
"The gap at the moment is a big advantage for Man City but there is a long, long way to go."