David Beckham was unable to stop Internazionale running out 2-1 winners in the Milan derby at the Giuseppe Meazza.
Goals by Adriano and Dejan Stankovic put Inter two up in the first half and Jose Mourinho's side looked to be cruising to all three points before Alexandre Pato's 71st minute strike pulled one back for Milan and ensured a nervy final 20 minutes for the Nerazzurri.
The result saw the reigning champions of Italy take a huge step towards reclaiming their title after opening up a nine-point advantage over their nearest rivals Juventus, who were held to a 1-1 draw by Sampdoria earlier in the day.
Milan remain in third but the defeat dealt their Scudetto hopes a major blow - the Rossoneri now trail their city rivals by 11 points.
Despite the hype prior to kick-off, Beckham had a minimal impact on the game and the former England captain was substituted on 58 minutes, although his withdrawal appeared enforced by a hamstring injury.
The other subject of pre-match excitement, Paolo Maldini, defied his 40 years to play an integral part in what was his last Milan derby, even though his defence was breached twice before the end of the opening period.
Inter stormed out of the blocks and Zlatan Ibrahimovic was presented with a great chance to open the scoring inside the first minute when Esteban Cambiasso's free-kick found him unmarked six yards out. But the erratic Swede, who is just as capable of infuriating as he is of astounding, misjudged the flight of the ball and headed over the bar.
But his profligacy in front of goal was overshadowed by a far worse miss by Stankovic 18 minutes later. Cambiasso was again the architect, sliding the ball across to the Serb who inexplicably took a touch when a first-time shot was all that was required. The delay allowed Massimo Ambrosini to get back and make a crucial intervention and the chance went begging.
Stankovic was to make amends soon enough, but not before Adriano broke the deadlock on 29 minutes, albeit under controversial circumstances.
The Brazilian appeared to handle the ball as he bundled it over the line from Maicon's wickedly teasing cross, but the referee's whistle sounded only for a goal and not for the infringement Milan keeper Christian Abbiati was screaming for.
Fourteen minutes later and Inter had doubled their lead, Stankovic putting his earlier hesitation well behind him to fire home first-time from Ibrahimovic's knock down.
Two-nil down and Milan had a mountain to climb to get back into the game, one that nearly became much steeper soon after the break when a slip from Kakha Kaladze let in Adriano, only for the Brazilian to send his shot wide of the mark
Adriano turned creator moments later, playing in Ibrahimovic who was denied by a fine fingertip save by Abbiati.
Inter were in complete control of the game and seemingly set for a comfortable victory but once Pato had latched onto Marek Jankulovski's cut-back from the by-line and found the back of the net, the complexion of the game altered dramatically.
Gone was the swagger the home side had been playing with while Milan were rejuvenated and poured forward in search of an equaliser as the half progressed.
The introduction of Pippo Inzaghi for Beckham presented Inter with a real headache, the veteran striker posing a constant threat with his penchant for hanging off the last defender and his predatory instincts.
The 35-year-old had the ball in the back of the net of 78 minutes, only to see his rocket into the roof of the net chalked off for offside, and he went close again with a header with eight minutes remaining.
In between those chances, Pato brought a save from Julio Cesar with a low strike but the final chance of the game fell to Inzaghi as the closing stages of the match began to resemble a siege on the Inter goal.
Julio Cesar came to Inter's rescue again however, and Inter held on to close in on a fourth Scudetto success - and claim bragging rights in Milan at least until next season.