There will be jollity among the jangling nerves at the King Power Stadium on Sunday as Premier League leaders Leicester City resume their improbable pursuit of the title against Southampton.

Leicester chairman Vichai Srivaddhanaprabha, who celebrates his birthday on Monday, is offering a free doughnut and bottle of beer to every home fan in attendance.

"It's his birthday and he wants to offer some beer and something more," explained manager Claudio Ranieri. "It's fantastic."

After pizzas for clean sheets and a locally produced sausage named 'The Ranieri', Srivaddhanaprabha's doughnut giveaway is the latest culinary complement to Leicester's extraordinary season.

There has been plenty to please the palate at the King Power since the campaign began and the champagne will soon be on ice if Leicester's magnificent form continues.

Their lead currently stands at five points and with second-place Tottenham Hotspur travelling to Liverpool on Saturday -- where they have won just once in 21 league visits -- Leicester could conceivably find themselves seven or eight points clear by bedtime on Sunday.

With seven matches remaining, it is a dizzying position for a club that has never previously won the title and Ranieri is determined to keep his players focused on the task in hand.

Asked if the next six weeks will be the most important in Leicester's history, the Italian replied: "Yes, of course, because never have Leicester been at this level at the end of the season.

"But now for us it's important to be focused on the next match. Step by step, match by match.

"It will be a difficult match, but I hope with our support we can do a good performance."

As the finishing line draws closer, Leicester are showcasing the kind of obdurateness typical of title-winning teams.

Four of their last five matches -- against Norwich City, Watford, Newcastle United and Crystal Palace -- have been won by a 1-0 scoreline, with Riyad Mahrez netting the winner at Palace in their last game before the international break.

No less qualified an observer than former Manchester United manager Alex Ferguson has described it as the form of champions.

Leicester displayed similar resolve in October's reverse fixture at St Mary's, battling back from 2-0 down to draw 2-2 thanks to a second-half Jamie Vardy brace that included a 91st-minute equaliser.

Southampton manager Ronald Koeman is full of admiration for Ranieri's achievements, but having seen his side come from 2-0 down to beat Liverpool 3-2 on their last outing, he knows that his players have plenty of grit of their own.

"All the credit to them that they are still fighting to win the title," the Dutchman told his pre-game press conference.

"Maybe this weekend will be the big decider, if you have Liverpool-Tottenham and Southampton against Leicester.

"But they are also afraid about Southampton, because they know we can beat everybody. We showed that against Liverpool, away against Manchester United (a 1-0 win), away against Chelsea (a 3-1 win).

"We are full of confidence to play, but we realise that they are very tough and very strong, with some great individual players."

Having put a mid-season slump behind them, Southampton are nurturing their own lofty aspirations, with just three points separating them from the Europa League positions ahead of the weekend action.

Forward Shane Long is Koeman's only injury doubt, having gone off with a patellar tendon injury after scoring in the Republic of Ireland's 2-2 friendly draw with Slovakia in Dublin on Tuesday.

But left-back Ryan Bertrand is fit despite withdrawing from the England squad with a knock, along with forwards Charlie Austin and Jay Rodriguez, both of whom were recently sidelined by injury.

Leicester could be without left-sided player Jeff Schlupp, who sustained a knee injury on international duty with Ghana, while midfielder Matty James is unlikely to feature after a long-term knee injury.