Brazilian defender pops up with a stoppage time header to claim a shock draw for the Serie A title-holders in Camp Nou
Pedro and David Villa were the host's heroes as they netted a goal either side of half-time to cancel out Alexandre Pato's early opener.
But, in the third minute of stoppage time, Thiago Silva popped up inside the box to meet Clarene Seedorf's corner with a powerful header which flew into the net to snatch a late point.The match began in absolutely extraordinary fashion when AC Milan surged into a 1-0 lead with just 24 second on the clock.
Pato picked the ball up virtually from kick-off, knocked the ball through the centre of the Barcelona defence and accelerated directly towards goal leaving Sergio Busquets trailing in his wake before slotting a cool finish under the advancing Christian Abbiati.
The early goal was exactly what the doctor ordered in terms of Massimiliano Allegri’s tactical plan, as it allowed his team to sit deep, defend in numbers and attempt to utilise Pato’s pace on the counter attack.
For a 20-minute spell following the goal the visitors defended doggedly while testing the Barcelona rearguard, particularly the nervy Sergio Busquets, with a handful of lightning counter attacks.
Meanwhile, back at the other end, their luck was also holding out as Lionel Messi forced at least four decent saves from Abbiati before striking the outside of post with a free-kick from 25 yards.
However, as the half wore on the game was almost exclusively played in the Milan half of the field, and, despite their organised and disciplined defending, one moment of magic from Messi in the 35th minute proved their undoing.
The Argentine flicked the ball between Alessandro Nesta and Ignazio Abate and darted through the gap between the pair. He then proceeded to shrug of Abate’s weak challenge and prodded the ball across the face of goal to gift Pedro the easiest of tap-ins.
Tormentor| Messi causes trouble for the Milan defence
Milan’s stubborn resistance was breached for a second time five minutes after the restart, and this time there was little anyone in the Rossoneri ranks could do to prevent it as Villa curled a sublime free-kick into Abbiati’s top right-hand corner from 25-yards out.
The rest of the second period played out in a predictable fashion, with Barcelona in complete control of possession, but surprisingly they lacked penetration in the final third as Milan defended doggedly.
Despite the home side's control and pressure it was the visitors who sprung a final suprise as Silva powered home a bullet header in the third minute of stoppage time to grab a share of the spoils.
Barcelona now travel to Belarus to meet Bate Borisov, while Milan host Viktoria Plzen at the San Siro in the second round of group matches.