The goalkeeper was stretchered off with an apparent knee injury: Chelsea fear it is an anterior cruciate ligament problem which could see him ruled out until the summer.

Inter were ahead as early as the third minute, Diego Milito finishing inside the near post.

Chelsea dominated large swathes of the encounter and equalised straight after half-time when Salomon Kalou fired into the corner from 20 yards.

However the lead lasted only four minutes, Esteban Cambiasso volleying low into the corner.

It was a whirlwind start from Jose Mourinho's Inter, one rewarded inside three minutes. A clever pass down the channel from Samuel Eto'o found Milito in space on the left side of the box after Wesley Sneijder's run caused confusion in the Chelsea defence.

The Argentine moved the ball inside with John Terry left standing and fired past the helpless Cech.

The Blues could have been level on 15 minutes when Michael Ballack, who had been in the wars with a facial wound due to a high Thiago Motta boot, was fouled by Dejan Stankovic almost 40 yards out: Didier Drogba unleashed a ferocious free-kick that cannoned off the underside of the crossbar.

Carlo Ancelotti's side played constantly inside the Inter half but clever movement from their hosts' strikers often saw Terry and Ricardo Carvalho stretched apart, while right-back Branislav Ivanovic was most vulnerable on the flanks despite the presence of winger Florent Malouda in an emergency left-back spot.

Milito was correctly booked for diving in the box while at the other end on the stroke of half-time another penalty appeal was less clear-cut.

A hurled Ivanovic throw put Kalou in following the slightest of touches from Javier Zanetti, and the wrong-footed Walter Samuel challenged the Ivorian from behind as he entered the six-yard box.

No penalty, said referee Manuel Mejuto Gonzalez - it was 50-50 whether there was enough contact to warrant Kalou going to ground.

Anelka looked lost playing from deep while Drogba's passing in the final third was poor; at the other end Eto'o fared little better when chances were created, missing with a swinging left foot eight yards out with the goal at his mercy.

The second half continued as the first had ended, the cautious passing from the visitors broken when Ivanovic again marauded forward. He made it as far as the penalty area before the ball broke to Kalou - and Julio Cesar, hurt in a car accident last week and sporting bruises under both eyes, took too long to go to ground as the swerving shot found the bottom corner.

If Chelsea's travelling fans thought they would go on to win, they were wrong. Inter broke out of defence, finding Sneijder on the left, and when the ball dropped to the edge of the box Cambiasso was there to strike.

His first effort was blocked by Serb Ivanovic, but the second was unstoppable into the far bottom corner to send a disbelieving Giuseppe Meazza again into raptures.

Soon afterwards Cech went down clutching his leg and the home fans clapped him as he left on a stretcher, to be replaced by Hilario.

Of the Inter substitutes precocious teenager Mario Balotelli caused problems down the right as a livewire outlet among an XI who were extremely difficult for the West London outfit to break down.

When he did find space in the box Lampard was unlucky to see his shot saved by the legs of Cesar. The towering presence of Lucio prevented many other opportunities as Drogba was often left frustrated around the outside of the box.

Inter held on in the first European meeting between the sides - but Chelsea have a valuable away goal to take back to Stamford Bridge, where Mourinho will be given a hero's welcome.

If anyone believed his assertion last week that his intimate knowledge of the majority of this Chelsea side would hinder his preparation for the tie, they now know better.

Jonathan Symcox / Eurosport