Tottenham Hotspur were the first club to expose chinks in the armour of Pep Guardiola's Manchester City and the in-form north London side will seek to inflict further damage at the Etihad Stadium on Saturday.
When City travelled to White Hart Lane in October they did so with former Barcelona mastermind Guardiola threatening to turn his first season in England into a cakewalk after his side opened up with six straight Premier League wins.
A 2-0 defeat, which could have been heavier, proved not just a blip, but a huge reality check for the Spaniard whose side have never been the same since.
While Tottenham have emerged as serious title contenders, winning their last six league games to climb to second, seven points behind Chelsea, City have slipped to fifth following a 4-0 hammering at Everton last weekend.
Guardiola, who turned 46 on Wednesday, needs a quick response from a squad being derided as defensively fragile, ageing and struggling to adapt to his possession style of play.
City have managed to keep clean sheets in only 25 percent of their matches under Guardiola with goalkeeper Claudio Bravo, the man who edged England's Joe Hart out, and big-money central defensive signing John Stones, taking their share of flak.
Ten points behind Chelsea, Guardiola all but conceded that City were out of the title race after the Goodison Park debacle.
Spurs, on the other hand, could hardly be in better shape, even if Jan Vertonghen's ankle injury against West Bromwich Albion on Saturday took some gloss off their recent run.
Mauricio Pochettino's side have conceded only 14 goals in 21 league matches and are scoring for fun with 19 in their six-match winning streak, including Harry Kane's hat-trick in the 4-0 rout of West Brom.
Young England midfielder Dele Alli is also in a rich vein of form so Tottenham will head north confident of a first away win against one of their top-of-the-table rivals this season, having lost to Chelsea and Manchester United and drawn at Arsenal.
With City and Spurs facing each other, the other teams in the top six will look to gain some ground.
Chelsea will need to put aside speculation about striker Diego Costa's future when they host struggling Hull City on Sunday when fourth-placed Arsenal entertain Burnley.
Leading scorer Costa missed Chelsea's 3-0 win at Leicester City last weekend with a back injury amid reports of a bust-up with manager Antonio Conte and a possible 30 million-pound ($37 million)per year deal to play in China.
Costa did return to training this week and all eyes will be on the Spain striker's body language should he face Hull.
Third-placed Liverpool, below Tottenham on goal difference, take on bottom side Swansea City in Saturday's early game while Jose Mourinho's Manchester United, in sixth, go to Stoke City.