The full extent of his side's failure to take their chances in Port Elizabeth last night became known a few hours later when Mesut Ozil scored the goal that ensured Germany finished top of Group D.
It set up a mouth-watering revival of a long-standing rivalry, and reignited memories of 1966, 1970 and 1990.
Both countries are sure to be obsessed about the outcome, with Franz Beckenbauer already stirring the pot by claiming England have been "stupid" in allowing themselves to end up in a more difficult section of the draw.
But for an outsider like Capello, the actual opponent was not as important as his team discovering their form again.
"For me, who we play is not important," he said.
"What was important was to rediscover our spirit and finish first or second. Now we are into a play-off - and I think we are ready."
Capello believes England are ready because they managed to turn yesterday's clash into something more akin to a Premier League game, rather than the pedestrian strolls that have gone before.
Both Steven Gerrard and Frank Lampard were able to get forward with purpose and, after an initial slow start, James Milner excelled, delivering a succession of excellent crosses from his right-wing berth.
"The performance of the team was really important," said Capello.
"I saw the spirit we had lost in the games we played before."
For all the troubles of the previous days, the issues John Terry raised in public but was denied a chance to do so behind closed doors, for all the "big mistake" the Chelsea captain made, it seems a message got home.
It may have been the fairly simple realisation that England can only achieve their aims as a unit rather than unsettled individuals. But without doubt, there was a common goal, and it ensured the problems of previous games were resolved.
"We saw the games we played, the first half against Algeria in particular, and we understood that was not a good way to go forward," said Capello.
"Training was really good all the time. It was focused and fast. We found the physicality that we have known before, the physicality that we know in the Premier League."
Reproducing Premier League form continually is Capello's target now. The Italian has realised trying to engage in a slow, technical game is not the way for England to progress.
Better to adopt a quicker, more natural, style, accepting mistakes are inevitable but challenging opponents to keep pace.
They could however, do with being more clinical, if only to avoid the nervousness that scarred the final 15 minutes when Slovenia were hunting an equaliser that would have knocked England out.
"We created chances but we didn't score, so we had to suffer," lamented Capello.
"But that is normal at the World Cup."
It is hard to envisage Capello countenancing many changes, with only the central defensive slot alongside Terry up for grabs. After a shaky beginning, Matthew Upson improved as the match went on and was involved in that desperate late scramble to keep Slovenia at bay.
The smart money must be on the recall of Jamie Carragher though. Carragher missed yesterday's encounter through suspension but his greater experience is likely to be called for against opponents who can boast the attacking expertise of Lukas Podolski and Miroslav Klose, in addition to the youth of Ozil and Thomas Muller.
There could be a further defensive reinforcement on the way, if not for Sunday, then a potential quarter-final against either Argentina or Mexico in Cape Town on 3 July after Ledley King was spotted on the training ground this morning.
King suffered a groin injury during the early minutes of England's draw with the United States in Rustenburg on 12 June, since when he has been consigned to gym work.
Admittedly, King did not do any contact work, and was restricted to an individual session, but even his appearance has to be taken as a positive sign.
Rooney has struggled to impose himself during the tournament so far and was substituted after taking a kick on the ankle he originally injured on UEFA Champions League duty for Manchester United against Bayern Munich in April.
However, the damage is not thought to be extensive and Rooney should be available for the weekend.