Roberto Mancini may have committed the cardinal sin by promising something that is out of his hands, the Premier League title.
The 47-year-old may have a wealth of playing and managerial experience, but has shown a great deal of naivety in vowing to win a title that has gradually slipped from his grasp, from the moment his Manchester City side hit the Premier League summit in mid-October.
A five-point lead has now become a four-point deficit, with 10 games still to play, including a game in hand over leaders Manchester United.
As well as the table, the fixture list is unpleasant viewing for Mancini. Domestically, teams have succeeded when City's passing game has been disrupted, and a physical battle has ensued, and with Stoke City and Sunderland on the horizon, as well as Arsenal at the start of April, their title hopes could be extinguished before they face United at the end of next month.
However, the immediate challenge comes in the form of a side who have exposed how City can be derailed amid a physical confrontation already this season against Chelsea, who under Roberto Di Matteo have won their last four and are England's sole representative in European competition.
With City having lost two of their last three, and fallen foul of Sporting Lisbon in the Europa League, the game comes at a far from ideal time for Mancini's men, not least because of the improving form of Fernando Torres.
The Spaniard produced undeniably his finest performance in a Blues shirt against Championship side Leicester City in the FA Cup, scoring twice, but more importantly showing a turn of pace and desire we've seldom seen since his days at Anfield.
With captain Vincent Kompany, whose animalistic tendencies that work to combat an opponents disruptive approach proves so crucial, and Joleon Lescott, the most underrated facet of City's title challenge, both out injured, Torres has the ideal opportunity to prove his revival can be sustained. Chelsea's overwhelming valuation of Torres was because of his ability to win games of this stature; it's about time he produced when it mattered.
Such is the importance of Wednesday night's game that if they do fall short at home, where they last lost in December 2010, then it would drive a stake through their title chances.
A subsequent trip to the Britannia Stadium would leave no margin for error, while United will be handed the chance to increase their lead at the top come the visit of Fulham on Monday.
Mancini's experience mightn't be helping him in his pre-match comments to the written press, but even he will know defeat against Chelsea will leave his side's title chances spiraling out of his control.