After almost five months of the campaign, it is a fascinating duel: old hand against new kid on the block, old money versus new money, an established power against brash upstarts. After 20 matches apiece, there is little to separate the London rivals, little to suggest that either holds the whip hand.

Arsenal have shown more signs of weakness. Since their unbeaten 49-match league record bit the dust amid much acrimony and soup-slinging in the 2-0 defeat by Manchester United at Old Trafford in October, they have won only five of ten matches. The blip became a wobble then a slump, with Wenger, for once, sounding unconvincing as he attempted to explain the loss of form.

However, four wins in their past five outings, plus a 2-2 draw against Chelsea at Highbury, have silenced many of the doubters. Adopting a siege mentality that Sir Alex Ferguson and his United players would be proud of, Arsenal have dug in and called on all their renowned resilience. They are not ready to be dethroned just yet. Wenger said: “There is such a long way to go, with still two league games over the Christmas period and there is the Champions League to come as well.

“When you are on a bike, you put your head down and just go. Maybe in the last five or six games, you look to see who is around you. We are not at that stage.”

Chelsea have taken over the yellow jersey, not through an unrepresentative time-trial but by winning stage after stage. Initially cautious and short of goals, they caught the early Arsenal breakaway on November 6, when they went top of the Premiership, and have retained their position. United are still in sight of them both, Everton also, but a two-man sprint is developing.

“When you go top, it is important to stay there,” Mourinho said. “If you lose, you must not lose your next game. You must not go to second place or third. When we lost to Manchester City, we showed that. We won our next game. It was a big answer. After we arrived at the top, we showed we can deal with it. It is important to do this.”

Winning is already ingrained in the Chelsea players, a psyche born of 22 victories in 29 fixtures in all competitions this season. Mourinho has made his mark, so much so that he feels that his squad is on remote control, finely conditioned and disciplined in the manner of its master.

“At the start of the season, they needed me for them to believe that they can win the league,” Mourinho said. “Now they are confident, now they know that they can win it, they don’t need me for that belief. We are together and we are ready.”

The mind games begin, with Mourinho at his playful best. “Arsenal’s pressure is greater than ours,” he said. “They have to win and wait for our mistake. We don’t have to wait for their mistake, we just have to get our results.”

Ashley Cole, the Arsenal defender, conceded the point. “It’s hard for us to keep watching them win,” he said. “It’s a bit like banging our heads against a brick wall — them winning, then us catching them up. Hopefully, they’ll have a bit of a blip like we did and we can capitalise on it.”

The next ten league matches, from January to March, should prove decisive, although it is difficult to see where either side will drop points. Both will also be involved in the European Cup and Chelsea might be distracted further by the two legs of their Carling Cup semi-final against United. Their pursuit of the “quadruple” is relentless.

Who will take the big prize? The experienced campaigners or the bright young things? First-termer or sophisticated sage? Arsenal have been there, seen it, done it. Chelsea talk a good game and dream on. Take your pick.

CRYSTAL BALL

Predictions for the next ten matches

CHELSEA
Jan 1: Liverpool (a) D
4: Middlesbrough (h) W
15: Tottenham Hotspur (a) D
22: Portsmouth (h) W
Feb 2: Blackburn Rovers (a) W
6: Manchester City (h) W
12: Everton (a) D
26: West Bromwich Albion (h) W
Mar 5: Norwich City (a) W
19: Crystal Palace (h) W

ARSENAL
Jan 1: Charlton Athletic (a) W
4: Manchester City (h) W
15: Bolton Wanderers (a) W
23: Newcastle United (h) W
Feb 1: Manchester United (h) D
5: Aston Villa (a) W
14: Crystal Palace (h) W
26: Southampton (a) W
Mar 5: Portsmouth (h) W
19: Blackburn Rovers (a) D