London - Luiz Felipe Scolari has ordered an overhaul of Chelsea's defensive system in response to his side's crushing defeat at Premier League title rivals Manchester United.

Accepting full responsibility for Sunday's 3-0 loss at Old Trafford, Scolari said he would switch from man-to-man marking and return to a zonal system in an attempt to eliminate the defensive mistakes that have blighted the Londoner's recent performances.

Two of United's three goals on Sunday came from set pieces and poor defending also contributed to the other one in a defeat that has left Scolari under intense pressure ahead of Wednesday's potentially tricky FA Cup third round replay at League One Southend.

"What has happened is a lesson for us," Scolari admitted on Tuesday. "It is a problem because we give chances for all teams to score goals from set plays."

The Brazilian appeared to acknowledge that his players could be suffering from a crisis of confidence but, against a background of speculation that all is not well behind the scenes, he insisted he had their support.

"We have done well in 25 games and not well in five. I need to change something. I have changed the system to zonal and not man-to-man.

"The responsibility now is for the group and not one man. But if we talk about the mistakes all the time, maybe we make more mistakes.

"Mentally it is a problem. We lost many points from set-plays and mistakes. Now is the time to talk with the players about what is happening."

Scolari added: "We have conceded five goals in our last four games but it is more my mistake than the players' because it is my system.

"I tried to do zonal marking but changed it back to man-to-man sometimes, now we change the system again.

"I am responsible for us conceding the last two goals against United because I tried to change the result in the second half. I opened the midfield. I was wrong but this is my style."

There have been suggestions that the current Chelsea squad is now past its best with key players like Didier Drogba, Michael Ballack, Deco and Frank Lampard all in their 30s, or that Scolari lacks the ability to get them to perform at their best.

But Scolari insisted: "We are all in the same boat. If Chelsea lose a game it is not only Scolari, it is the Chelsea team.

"There is not a problem with the spirit. It is a problem of mistakes not spirit."

The Brazilian also dismissed reports of a bust-up with Nicolas Anelka, who has scored 16 goals in all competitions this season but has not started a match since December 26 because of Didier Drogba's return from injury.

"There has been no row with me," said Scolari, who has made it clear he does not think Anelka and Drogba will work as a strike partnership.

"Everybody thinks it is easy to play two strikers because they are good," he said. "But I try to prove to the people and for me and Chelsea, that is difficult.

"When one player is outside, as was Didier Drogba, he needs to play two, three or four games, and in that time I need to look at what's happened. Afterwards I have to decide."

Given how poorly Drogba performed against United, it seems probable that Anelka will be given a chance to impress at Southend.