Despite playing at home in front of a 75,000 crowd, coach Massimiliano Allegri was clearly aware of his team's limitations and accepted that his side would have to concede most of the possession to Barcelona.
The Catalans had enjoyed 65 percent of the ball before Milan opened the scoring in the 57th minute, just as Allegri had predicted they would before the match.
But, rather like Chelsea in last year's semi-final, Milan managed to nullify Barcelona's attacked by pulling all their players back into the last third of the defence, creating an almost impenetrable barrier.
It worked remarkably well and not even the combination of Andres Iniesta and Lionel Messi could find a way through.
"It was an extraordinary game from a defensive point of view as we didn't concede anything to Barcelona," Allegri said.
A season which started disastrously has suddenly come good for Milan as Allegri coaxes the best out of group of players who many thought would struggle to compete both domestically and in Europe.
Allegri's future was the subject of almost weekly speculation back in September and October, yet the unflappable coach is now the hero of the hour after his side became only the second this season to prevent Barcelona from scoring.
"We did very well and I have to say that our coach was very, very good in my opinion," said chief executive Adriano Galliani, who has stood by Allegri from the outset.
"We played a perfect match. We did well to prevent them from getting inside the box."
JEERED OFF
Wednesday's rapturous celebrations were a far cry from the opening Champions League match of the season when Milan were booed off the pitch at a half-empty San Siro after being held 0-0 by Anderlecht.
Forced to sell players such as Zlatan Ibrahimovic to cut costs, Milan failed to win a home game in their group and their total of eight points was the lowest of any of the teams in the last 16.
Yet the club appear to have spent wisely in the transfer market and players such as Kevin Constant, playmaker Riccardo Montolivo and teenage forward M'Baye Niang have all turned out to be astute signings.
Even Colombian central defender Cristian Zapata has come good after being relegated with Spanish club Villarreal last season.
Allegri has stressed throughout that Milan are building for the future rather than looking for immediate success.
"The team is still growing it's doing so very quickly, I think it's a team that will do well for years to come," he said.
The win brought more tributes to club president Silvio Berlusconi, the former Italian prime minister who is campaigning to return to power in the weekend's parliamentary elections.
"Football is beautiful as you never know what can happen, but not even the most optimistic fan would have imagined this," Galliani added.
"We have to dedicate this win to president Berlusconi as it's the 27th anniversary of his acquisition of the club a
