David Beckham admitted it would be "difficult" if he has to return to LA Galaxy after his loan spell at Milan comes to an end. Milan have officially loaned the 33-year-old until the end of the season but his parent club have demanded that he return on 9 March for the beginning of the MLS season. Milan remain confident they will sign Beckham on a permanent deal, however, and the player has remained unequivocal in his desire to stay.

"It would be difficult to go back after everything that has happened," said the former England captain after yesterday's Milan derby. "I have said that I want to stay but I will stay professional and do what I have to do."

Asked if his future would be decided in the next 48 hours, Beckham replied: "I don't know. Talks have been going on and on and everyone seems to be talking about it but it's out of my hands. We'll know more in the next week."

Beckham also confirmed that his performance here was hampered by a calf injury. "I had a kick against Spain on Wednesday and it didn't really clear up and I had another kick on the same place — my calf — tonight."

Beckham was only briefly effective before being replaced early in the second half, as Internazionale extended their lead at the top of Serie A to 10 points, and moved 11 clear of their city rivals. "We are quite far behind Inter now, we were quite far behind before the game started and we needed to win it," reflected Beckham. "But you never know, this league is up and down. There's a chance but it is a slim chance."

If Beckham's reputation is his currency, Jose Mourinho's is inflating. Significant factions at Inter would surely be happy if — as he has hinted — he was to walk away after delivering the Scudetto, but his suitors would be numerous. This was his 110th home game without defeat, a run stretching back seven years to his first season at Porto. Goals from Adriano and Dejan Stankovic put Inter 2-0 in front and they were dominant for over an hour. Alexandre Pato briefly unsettled the hosts with a sublime goal and Inter rode their luck when Filippo Inzaghi had a goal ruled out for offside, but Mourinho had made his point.

Italian football may have lost some of its lustre but it flexed its muscles last night. Kaka's ankle injury allowed Ronaldinho a start for Milan, yet Andriy Shevchenko was omitted entirely, as was Hernán Crespo from Inter's squad. Their advancing years can hardly be mitigation, with the two sides fielding a combined 20 players aged over 30 in their match-day squads.

Mourinho had said before the game that Serie A was "for people who love and understand the game". Yet Inter were the more direct side, redolent at times of Mourinho's Chelsea. Zlatan Ibrahimovic could have scored after a minute and Stankovic should have finished better when, five yards out, he hesitated long enough for Massimo Ambrosini to slide in with an astonishing cover tackle.

Inter's opening goal in the 29th minute punctured Milan's resolve. Maicon, the effervescent Brazilian right-back whose fitness was such a concern for Mourinho, crossed for his compatriot Adriano, who fluffed his header before cuffing the ball into the net.

Milan hardly protested but Inter were lifted with Maicon becoming the focal point of their play, tormenting his opposing left-back Marek Jankulovski. Inter's polished game was again evident at their second goal, as Ibrahimovic rose above Kakha Kaladze and placed a cushioned header into the path of Stankovic. The Serbian glided away from his marker before finishing sweetly from 15 yards.

By now Milan were becalmed, preoccupied by the deficit in both the derby and the league. There seemed to be no way back and Beckham, no longer able to call on his old reserves of energy, did not look like a saviour.

Neither did Maldini, the veteran of 1,028 matches in his 56th — and last — derby. The 40-year-old Milan icon was powerless as Ibrahimovic, Adriano and Inter exploited him mercilessly in their colour-coded lime-green boots.

At the other end Pato was horribly isolated, his twinkle-toed runs wrong-footing cover yet bereft of support.

Carlo Ancelotti, the Milan manager, had seen enough and on 57 minutes Beckham, dolefully patting his left leg, was replaced by Inzaghi. Pato seemed lifted, and responded with a sublime goal on 70 minutes. Ronaldinho pushed the ball towards Jankulovski, making a rare run down the left before squaring accurately for Pato to finish past Julio Cesar.

Milan had further chances, mostly for the brilliant Pato, and Inzaghi had an equaliser chalked off by the linesman's flag. Mourinho responded with a modern attempt at catenaccio and, while Milan fumbled for the keys, Inter held out for the win.