Andre Villas-Boas admitted speculation over his future would only intensify after Chelsea lurched to yet another defeat that left them in danger of Champions League elimination.

Villas-Boas watched his Blues produce their latest defensive horror show to lose their last-16 first leg 3-1 and pile the pressure on their beleaguered boss.

And he acknowledged afterwards his side had shot themselves in the foot yet again as they extended their winless run to five matches.

The Portuguese has repeatedly insisted he has the full backing of billionaire owner Roman Abramovich but this performance would have done nothing to convince the Russian to deliver the vote of confidence his manager now needs more than ever.

"Speculation will continue as the results don't happen," Villas-Boas said.

Having thrown away leads with alarming regularity both at home and abroad this season, Chelsea duly did so again as captain John Terry's injury absence continued to tell.

Juan Mata gave them the dream start but all three of Napoli's subsequent goals were the result of poor defending, even if Edinson Cavani's second carried suspicions of handball.

Villas-Boas said: "We have to solve these mistakes at the back.

"We need this concentration right and this efficiency right, for sure.

"At the moment, without John, a very important player for the team, we have suffered a lot of goals recently.

"We had improved a lot at the beginning of January, so we have missed John.

"But we have full belief in these players and we have to continue to work with them to get it right."

David Luiz's latest mistake was the most costly, gifting Napoli the third goal that made them firm favorites to win the tie.

"It's obvious that that player has become a target," said Villas-Boas.

"He's a fantastic young player with a big future ahead of him, and he has to work to try and be a bit better.

"We suffered three goals. If he's linked to one, he might not be linked to the other two."

As well as taking flak for standing by Luiz, Villas-Boas is bound to face criticism for his decision not to start either Frank Lampard or Michael Essien.

Much has been made of the Chelsea boss' relationship with Lampard in particular, but he insisted his team selection was purely tactical, while Ashley Cole did not start after only just recovering from injury.

"You can have your opinion but it was based on what was the best team in my thoughts," Villas-Boas said.

"Whatever explanation I give you, in the end it would be a fantastic explanation if we'd won the game.

"Any explanation is now useless given the result of the game, so there's no point."

Villas-Boas, who admitted one of the formations he had been toying with but did not end up using had been written on a piece of paper left at the team hotel, added: "I had a conversation with Ashley and Frank.

"Through the players that they are and the players with the experience they have, they felt they could have helped the team.

"That's perfectly understandable."

Only three teams have overturned a two-goal first-leg deficit in Champions League history but a defiant Villas-Boas said: "I want us to be the fourth."

He added: "It's a negative result, of course, but a result we are sure we can turn around at the Bridge due to the amount of chances we had."