Big-spending Chelsea host Newcastle United on Saturday knowing they probably have to win to preserve a five-point advantage over champions Arsenal.

Should Chelsea slip up, Arsenal could close in on the English Premier League leaders if they overcome struggling Birmingham City at Highbury.

Jose Mourinho's talented Chelsea side have taken 16 points out of a possible 18 in their last six matches while their London rivals have managed only six points over the same period.

Fourth-placed Manchester United, nine points adrift of Chelsea, are finding their form and welcome out of sorts Southampton to Old Trafford after the win over West Bromwich Albion last week put them on 27 points from 15 games.

Worryingly for their London rivals that is just two points shy of United's total at the same stage of the 1998/99 treble season and a point ahead of their tally when they won the title in 2002/03.

United made up two points on Chelsea and Arsenal last week and Mourinho is taking notice.

"Arsenal have a great group of players in their first team but after that they have young people. Talented but very young. Only Manchester United have a squad like ours, two mature players for every position," Mourinho was quoted as saying by the British media this week.

Newcastle manager Graeme Souness believes his team's visit to the home of Russian billionaire Roman Abramovich's high-flying team is like venturing into the lion's den.

"We're playing a team on Saturday who are at the top of their game... but we won't be going there with any fear," he told the Newcastle website.

"We will continue to play our football and hope that lady luck shines on us."

Newcastle, coming into form again in Europe and at home, are likely to provide Chelsea with a stern test despite the absence of Alan Shearer, Nicky Butt, Stephen Carr and Andy O'Brien.

Arsenal have stumbled off their pedestal and manager Arsene Wenger has had to take a long, hard look at his first team players to seek answers for why they have gone off the boil.

Some commentators have even linked the slump to the loss of form of the French contingent.

Robert Pires and Thierry Henry have been below par and both have complained of injuries that have dogged their performances.

Wenger must find a winning formula soon if his side are to maintain their challenge beyond the New Year.

Ferguson wants his United side to start cranking up the pressure on the top two and hopes they can cut the gap as they prepare to face three teams in the bottom half of the table - Southampton, Fulham and Crystal palace -- among their next five league matches.