Viking Stavanger became the latest side to embarrass Chelsea in Europe, their 4-2 win echoing the achievements of Hapoel Tel-Aviv and St Gallen in the last two seasons.

"I don't know what to say, I really don't," Gianfranco Zola told the club's official website.

"I feel sorry for all the fans who made the trip."

Striker Jesper Gronkjaer echoed Zola's sentiments when he said: "We're all deeply disappointed.

"I feel really sorry for the fans who travelled so far and then we had such a performance."

Gronkjaer said Chelsea were disappointing in all departments.

"Poor defending, we should have scored more goals, I should have scored. We created so many chances but we've scored only two," said the Danish international.

Chelsea fielded a makeshift defence with John Terry making his first appearance of the season in central defence alongside teenager Robert Huth.

But coach Claudio Ranieri supported his players, despite his disappointment at conceding four goals.

"I am not angry with my defenders," he said.

"They are young, we had to make too many changes and they were not in the best condition.

"I am very happy with the performance of my players.

"Of course I am not happy because we conceded four goals and that is strange for Chelsea.

"We played well and dominated the game but we made a lot of mistakes and gave them four goals as presents.

"I am very disappointed, as manager I take a lot of responsibility."

Viking boss Benny Lennartsson - the former manager of Bristol City - said Chelsea's defeat was "nothing to be proud of" as he rubbed salt into Ranieri's wounds.

"Losing to a Norwegian team is nothing to be proud of," said Lennartsson.

"If you score four goals when you play a team like Chelsea then you must be satisfied, and I shall go home and open a very good bottle of red wine tonight.

"Even if we only go through one round, like we did last year against Kilmarnock, it will be an achievement, although it is a different story to knock out a team like Chelsea."

And Viking's Erik Nevland, who scored twice including the 87th minute decider, said Chelsea lacked fighting spirit.

"Chelsea wanted to outplay us all the time, but maybe they could learn a bit from us in terms of fighting spirit," he said.