Claudio Ranieri's second game in charge of Chelsea saw them embarrassingly knocked out of this competition by St Gallen of Switzerland.

A year on and the chances of a first-round banana skin look remote as two goals from Eidur Gudjohnsen and an injury-time strike by Frank Lampard set up the London side nicely for next week's second leg visit to Sofia.

Having admitted his side are probably not ready to win the league title this season, Ranieri's imperative is to secure Chelsea a lucrative Champions League spot to help offset, and justify, the £32m sterling outlay on new players in summer.

Failure will put his job on the line. But to achieve success the coach will need to avoid a repeat of last night's team problems.

His top striker Jimmy Floyd Hasselbaink was suspended, and Marcel Desailly was absent with an ankle knock. William Gallas, signed for £6.2m, took his place.

With Jesper Gronkjaer also out injured, Lampard was moved to an unfamiliar position out wide on the left while Chelsea's problems mounted just before the half-hour when Emmanuel Petit went off with a chest problem.

Despite all the rearrangements Chelsea dominated the first half and Gudjohnsen enabled them to go in at half-time a goal up. Seconds into injury time the Icelander, making his first start of the season, received a Graeme Le Saux's throw-in about 20 yards out, turned inside, sprinted between two defenders, juggled the ball and chipped the goalkeeper for a virtuoso solo goal.

Levski's defence had looked well-drilled, but their ability to counter-attack rarely troubled Ed de Goey in the first half, though just before Chelsea's goal Konstanin Golovskoy unleashed a piledriver which the goalkeeper acrobatically turned over the bar.

Chelsea began the second half by switching their system to 3-5-2 to mirror the Bulgarians. Lampard took up a more comfortable position on the right, Zenden moved inside and Le Saux, who had already been finding space down the left, pushed forward.

It almost paid immediate dividends. For once Le Saux put in a decent cross and Zola, nipping in front of a defender, directed his header just wide. Substitute Jody Morris chipped just over before Zola's impudent backheel released Lampard, whose pass to Zenden was wasted by the Dutchman. Morris then had a penalty appeal for handball turned down.

Chelsea's movement in front of goal was now causing all sorts of problems and they added a second on 73 minutes. Petkov's diving save from Zenden's header forced a corner which Zola swung over on to the head of Gudjohnsen. The goalkeeper got a hand to the ball but could only help it into the net.

CHELSEA (4-4-2): De Goey; Melchiot, Terry, Gallas, Le Saux; Zenden, Jokanovic, Petit (Morris, 29min), Lampard; Zola, Gudjohnsen.

LEVSKI SOFIA (3-5-2): Petkov; Markov, Stoilov, Topuzakov; Stankov, B Ivanov, Golovskoy, Genchev, Stoyanov; Chilkov (Pantelic, h-t), Botelho.

Referee: H Fleishcher (Germany).