For once this season, a big night did not belong to Lionel Messi. After 90 minutes of largely one-way traffic, San Siro rose to acclaim Luca Antonini, Milan's 29-year-old left back, who had thrown himself in the way of the best efforts conjured by Barcelona's resident genius and the rest of their wonder-team.
Milan were all smiles at the end of this goalless draw, and no wonder. If you can spend 90 minutes successfully neutralising a player who is on a run of 18 goals in eight games for the best club side in the world, you are entitled to consider the job half-done. Antonini and his fellow defenders tracked and shadowed and blocked to immense effect, preventing Messi from scoring or at least inspiring the goals that would have eased Barcelona's task in the return leg at the Camp Nou.
Their ferocious concentration on closing off the central areas paid dividends, denying the little Argentinian the opportunity to capitalise on the vast amount of possession enjoyed by his side. The one time he had the ball in the net, after beginning a move that also involved Xavi Hernández and Dani Alves midway through the first half, he had been too quick to sprint for the return and was correctly given offside.
As a result, Milan will not be unduly pessimistic about their chance of finding a way through to the semi-final in next week's return leg. Having given a convincing impersonation of an away team on their own pitch last night, they will hope that Barcelona succumb to the temptation to press even harder and allow them more scope for swift counters.
The two teams had already met in the competition this season, Barcelona getting the better of their two group matches with a 2-2 draw at the Camp Nou and a 3-2 win at San Siro. Barcelona's previous visit, in the semi-finals back in 2006, resulted in a 1-0 win, and last night's stalemate means that Milan still have not beaten the Catalan club on home ground since 2004.
The most dissatisfied Milan player last night should have been Zlatan Ibrahimovic, whose resentment of what he considers to be unfair treatment during his single season at Barcelona continues to fester, although sure there are not many who would share his amazement that Pep Guardiola favoured Messi ahead of the Swede as the spearhead of his attack. Yet Ibrahimovic's careful header across the six-yard box should have led to Milan taking the lead in the third minute, but an unmarked Robinho sent his volley flying over the bar from virtually point-blank range, with Victor Valdés helpless.
Four minutes later Messi slipped while taking a free kick after Nesta had fouled him a couple of yards outside the box. The television replay showed that a green laser had been directed on to Messi's face, clearly bothering him as he prepared to take the kick, which looped gently over the defence and almost fell at Seydou Keïta's feet.
Barcelona were already exerting a virtual monopoly of the ball and Alves was the next to experience the green laser treatment, again as Messi readied himself to take a free kick. It turned into a cute routine from which Alexis Sánchez might have won a penalty had he not made such a production of exaggerating his dive when caught by Christian Abbiati's foot.
Ibrahimovic's best chance of the night came when he ran on to Clarence Seedorf's perceptive pass in the 20th minute, but a half-hit shot from close range found its match in Valdés's alert dive. The Milan coach Massimiliano Allegri will be hoping that his strikers are in sharper form next week, when they will need to exploit the merest sniff of a chance to the full.
Well aware that they would be forced to endure the usual Barcelona tiki-taka torture, Milan concentrated on packing the main highway down the middle of the pitch, knowing that, with Carles Puyol deputising for Eric Abidal on the left, Alves represented the only real wide player in the visitors' line-up. How well the ploy worked could be seen 10 minutes from half-time, when Antonini made his first notable contribution. Beaten by Sánchez, he refused to give up, recovering brilliantly to catch the Chilean international in time to block his attempt to beat an unprotected Abbiati.
The half ended with Barcelona having failed to capitalise on all that possession, their frustration evident as Andrés Iniesta blazed a shot wildly over the bar from 30 yards. The diminutive midfielder returned to the theme a minute into the second period, scampering in from the left to send a better shot skimming past the post from 20 yards. But he seemed generally off-colour and was replaced with 15 minutes to go by Christian Tello, a 20-year-old Spanish striker who has recently begun to force his way into the team.
It was Tello who, with two minutes of normal time left, came closest to sending Barcelona home happy but instead ensured that Antonini's night would end in hugs and kisses.
When Abbiati turned Messi's shot into the young forward's path, the right-back once again anticipated the trajectory, rising with fists raised in a gesture of defiance echoed by 70,000 home fans. They were saluting the sort of resistance that once characterised Italian football. Not pretty, perhaps, but on this occasion Milan were happy to allow their guests to go home with the marks for artistic impression.