For having seen two-goal Teddy Sheringham wipe out David Connolly's penalty and then Keith Gillespie's stunning volley, the Hammers striker squandered a fantastic chance to secure the victory that would have eased his side's play-off qualification jitters.
And, if the newspapers are to be believed, win, lose or draw Alan Pardew – now without a win in five games – faces an anxious weekend with Gordon Strachan reportedly being lined up to replace him in the hot seat.
Both teams may have also drawn earlier this week, but the Hammers' point in the 1-1 stalemate with Crewe had come in far less less satisfactory circumstances than the one gained by comeback kings City in their 2-2 draw at Watford.
Certainly, the last thing the under-fire Upton Park boss needed was to find his inexperienced central defensive pairing of Elliott Ward and Anton Ferdinand up against Leicester's wily old Foxes Dion Dublin and Connolly.
For many, it was an accident simply waiting to happen and, when Stephen Hughes burst clear of the absent West Ham defence on 25 minutes, exposed Hammers keeper Stephen Bywater was lucky to escape with just a yellow card after crudely slide-tackling the fleeing midfielder as he looked all set to score.
City did not have to wait long to break the deadlock, though, for ex-Hammer Connolly – who had stung his former club in that draw at Watford – also returned to haunt West Ham as he drilled the subsequent penalty straight down the middle.
However, with an exasperated, exhausted East End crowd starting to bay for blood, West Ham took just three minutes to silence the boos as Mark Noble found Harewood whose right-wing centre to the far post was met by Sheringham who got in front of Darren Kenton to comfortably plant his six-yard header past former Spurs team-mate Ian Walker.
Having levelled, West Ham grew in confidence as they looked set to finish the half the stronger
But when Walker launched the ball upfield just a minute before the break, Ward out-jumped Dublin only to see Gillespie meet the headed clearance with a spectacular, angled 25-yard volley that bounced in front of the diving Bywater before nestling in the back of the lethargic keeper's net.
Pardew shuffled his pack at the interval, bringing on Sergei Rebrov for the ineffective Luke Chadwick, but it looked like summing up the Hammers night when the Ukrainian hobbled away after just six minutes to be replaced by Bobby Zamora.
And when Sheringham blazed high over from 10 yards, again West Ham must surely have thought that it was not going to be their evening.
It was not long, though, before the 38-year-old striker was atoning for that miss. For after winning the ball in midfield, Sheringham collected his pass back from Zamora and tucked a low 15-yarder wide of Walker into the bottom left-hand corner to claim his 18th goal of the season.
Both Noble and Carl Fletcher then went agonisingly close with long-rangers that were just inches off target, while Harewood's stinging volley was well gathered by the Foxes keeper.
Walker was saving the best until last, though, for when Noble's close-range shot was handled on the line by the consequently dismissed Nikos Dabizas, the casual Harewood – who takes the West Ham spot-kicks alternately with Sheringham – paid the price for his two-step walk-up.
The Foxes keeper saved the well-telegraphed penalty at the base of his left-hand post to protect that point for ten-man City, who also lost Jordan Stewart with a dislocated shoulder in West Ham's late, albeit fruitless, siege.