Mourinho's side have reached the summit despite just 11 league goals this season from their three main strikers, Fernando Torres, Demba Ba and Samuel Eto'o, but fortunately for the Blues their Belgium midfielder Eden Hazard has been in sublime form.
Hazard has netted 12 times in 26 league appearances, while also setting up countless chances for his team-mates, and boss Mourinho recently lauded the 23-year-old as Europe's most talented young player.
Chelsea defender David Luiz has also been impressed by Hazard's rise since moving to the Bridge from French club Lille in 2012 and the Brazilian is confident his team-mate can one day surpass Lionel Messi and Cristiano Ronaldo as the best in the world.
"He can be one day the best player in the world," Luiz said. "I'm so happy for him, because he's a great person, a great guy, with a lot of talent."
The Gunners are one point behind their London rivals and will be desperate to bounce back from their midweek Champions League defeat when they host Sunderland.
Arsene Wenger's side were left cursing their luck after losing 2-0 against Bayern Munich in a match where Mesut Ozil had a tame early penalty saved and goalkeeper Wojciech Szczesny was then sent off.
"We will concentrate on Saturday now, because we are going through a period with a lot of games," Mertesacker said.
"We will switch off from the Champions League now, and then switch on again for the Premier League on Saturday.
"We need that because we have played a lot of games. Our team has great spirit and will come back from this. Now we must keep our chins up."
Like Arsenal, third-placed Manchester City also suffered Champions League heartache in a 2-0 home defeat against Barcelona that left Manuel Pellegrini's team faced with probable elimination.
City, currently three points adrift of Chelsea, must put that result behind them quickly when they host Stoke City this weekend.
Reds boss Brendan Rodgers insists he would be happy with a top-four finish this season, but Liverpool are in superb form in the league and captain Steven Gerrard puts some of that down to teenage winger Raheem Sterling.
The 19-year-old scored a brace in the 5-1 demolition of Arsenal earlier this month and Gerrard feels Sterling is sure to have caught the eye of England manager Roy Hodgson, who will be mulling over the options for his squad ahead of the finals in Brazil.
"Raheem has been in great form over the last couple of months and I'm sure Roy is watching him very closely," Gerrard said.
"The Arsenal game was an unbelievable performance from a guy of that age.
"Now he has to do it every week. If he gets that consistency, he is going to be a frightening talent."
Manchester United's fall from grace this season has been dramatic and, ahead of their trip to Crystal Palace, there was another sign of the champions' decline as Juan Mata was forced to defend his new club against claims that their struggles will dissuade other top players from coming to Old Trafford.
David Moyes' men are 11 points behind Liverpool in the race to qualify for the Champions League, but former Chelsea playmaker Mata said: "I don't know what will happen in the summer but the manager said the other day at a press conference that he's going to be signing players.
"I think this club is at a stage of change, but I can tell you that the best players in the world will always arrive."
Liverpool v Swansea
Newcastle v Aston Villa
Norwich v Tottenham