Surely nobody would have predicted that the Foxes would be 17 points clear of reigning champion Chelsea after just 15 games.
But a superb 3-0 win for the Foxes Saturday at Swansea City, combined with a 1-0 win for promoted Bournemouth at Chelsea in the late kick off, a stunning upset, has left the table with an air of unreality.
And the wins for the underdog continued Sunday as Newcastle beat Jurgen Klopp's in-form Liverpool 2-0.
Algerian international Riyad Mahrez grabbed a hat-trick in Leicester's victory, substitute Glenn Murray's late header left Chelsea in 14th place with pressure re-applied on manager Jose Mourinho.
For once, Mahrez's teammate Jamie Vardy was not on target, his run of consecutive scoring in the EPL ending at 11 games. It is a record for the EPL but he failed to match the all-time 83-year-old record of Jimmy Dunne for the top-flight of English football.
Vardy showed rare nerves in wasting a golden opportunity in the first half at the Liberty Stadium but played a key role for teammate Mahrez for two of his strikes in an emphatic victory.
"The perfect day," Mahrez told Sky Sports as he took his personal tally to 11 in the EPL this season.
"Vardy didn't score, but he played for the team and the team is the leader," said Ranieri.
Bournemouth, with only two wins all season, took the game to Chelsea at Stamford Bridge and had the better of the early chances with the returning Thibaut Courtois tested.
Chelsea, bidding to get its season back on track, pushed forward more purposefully after the break, but could not make the breakthrough and Murray popped up to head the winner after Courtois had failed to punch clear a corner.
With 15 points from 15 games, Chelsea is only three points clear of the drop zone in an incredible reversal of its dominant form of last season.
Mourinho admitted a top four finish for Champions League qualification would now be tough.
"Before this game it was realistic to think that our quality would take us out of this position, but maybe now we have to think about top six," he told Sky Sports.
"I am concerned, of course. There is no chance that Chelsea will be fighting relegation. That is not the problem. It is that our objective is to finish top four."
While talk of the winning title may be fanciful, Leicester is taking advantage of inconsistent form by previous leader Manchester City, which was beaten 2-0 by Stoke in the early game Saturday.
Xherdan Shaqiri set up Marko Arnautovic for two early goals for Stoke, which dominated against a lackluster City team, despite welcoming back David Silva to its starting lineup.
Arnautovic should have completed his hat-trick but wasted other openings. "It was a disappointing start and we could not recover from it," England goalkeeper Joe Hart said.
Its city rival Manchester United could not make up much ground, held goalless again in a 0-0 home draw by West Ham, leaving Arsenal as the main challenger to Leicester.
The Gunners beat struggling Sunderland 3-1 at the Emirates with two second half goals from Olivier Giroud and Aaron Ramsey sealing the three points after a Giroud own goal had canceled out Joel Campbell's opener for the host.
Tottenham Hotspur extended its unbeaten league run to 14 games, but was held 1-1 at West Bromwich Albion after Dele Alli had put them ahead at the Hawthorns with a fine volleyed goal.
James McClean leveled for the Baggies before half time with a powerful header after an excellent home move.
In other matches, Watford continued its fine return to the top division with a 2-0 home win over Norwich, while bottom side Aston Villa grabbed a valuable point in the 1-1 draw at Southampton.
Sunday's sole match saw a priceless victory and three points for Newcastle, which is up to 18th, but on the same points tally as Norwich and Bournemouth in the early battle to avoid the drop.
It will likely relieve the pressure on Magpies boss Steve McClaren, his side's third win of a stuttering campaign.
Liverpool had won seven of its last eight games, but was consigned to only a second defeat in 12 under Klopp.
Georginio Wijnaldum's injury time strike after combining with Moussa Sissoko sealed the three points, his seventh of the season.
His earlier shot after 68 minutes was turned into his own goal by Martin Skrtel for Newcastle's opener.
Alberto Moreno was unlucky to have his effort chalked off for offside and Daniel Sturridge also came close to the equalizer for Liverpool after coming off the bench.
Klopp believed his side, fresh from a 6-1 League Cup thumping of Southampton in midweek, deserved a point, while McClaren said the win was "absolutely huge" after conceding eight goals in the last two games.