Two goals apiece from Frank Lampard and Nicolas Anelka plus others from Florent Malouda, Michael Ballack and Ashley Cole, set the seal on a fabulous attacking performance from Carlo Ancelotti's side.

Sunderland managed consolation goals from substitute Bolo Zenden and Darren Bent but the victory kept Chelsea one point clear of Manchester United at the top of the Barclays Premier League with a game in hand on their rivals.

Cole, who hit the post and set up Ballack's goal, was almost back to his brilliant best.

The England midfielder's contract expires in the summer and he is hoping to earn a place in Fabio Capello's squad for the World Cup finals in South Africa.

There has been much speculation over the midfielder's future at Stamford Bridge, but Buck believes that contract negotiations with the player will be concluded sooner rather than later.

"I am personally a big fan of Joe Cole and we are in discussions with his agent and hopefully that will be sorted out soon," said Buck.

Buck also hinted that Chelsea would not be adding to their squad in the current transfer window.

The Blues were banned from signing any players for two transfer windows after FIFA found them guilty of inducing teenager Gael Kakuta to breach his contract with Lens three years ago.

But the Court of Arbitration for Sport suspended the punishment ahead of their appeal.

"With regards to January, we asked for the transfer ban to be suspended as an option because several months ago we didn't know if we were going to have any injuries or great opportunities for us to buy a player," added Buck.

"We have only used the January transfer window a couple of times. You don't buy players just to buy players, you buy them to fill the need or because they are a better player than the one we have in a particular situation.

"A player really has to suit us for us to buy him, and then, even if a player is available, he has to be available at the right price."

Chelsea were unstoppable against Steve Bruce's Sunderland with Anelka scoring twice on his return to the side following a hamstring injury.

He was preferred to 20-year-old Daniel Sturridge, who scored twice in the previous 5-0 demolition of Watford in the FA Cup third round.

But former Manchester City striker Sturridge, who will cost Chelsea £3.5 million following a Premier League tribunal judgement last week, insists he will always have something to prove to someone as he battles to make his name at the club.

"I'm still young and while the pressure isn't a problem for me, I don't want people to expect too much from me straight away because I need time to develop like very young player," said Sturridge.

"You cannot rest on your laurels. There's always someone you have not proved yourself to after every good game you play. So, you have to aim to prove them wrong the next game and show people what you can do, but I don't think you're ever going to please everybody."

Sunderland boss Steve Bruce is adamant that when his injured and suspended players return, his side will get their season back on track.

Sunderland were without first eight first-team players and have now failed to win in the league for eight games but Bruce said: "I don't like making excuses. We were beaten by a very good team and it hurt.

"I could not fault the players for their effort but we could not cope without our big players. But we have to earn our corn when things are not good.

"We have to respond. I am confident we will do that and it will be better next week. I have lost as a manger by seven and have suffered it as a player but we will get our season back on track.

"I don't think I've picked the same back four for months and there were too many square pegs in round holes against Chelsea.

"We had a great start to the season and when we get our injured and suspended players back, it will be ok."