After Dean Ashton had wiped out Roque Santa Cruz's opener, the rookie teenager stepped off the bench to head the Hammers to a victory that moves them to within just three points of eighth-placed Blackburn Rovers.
Coming into the game on the back of hammerings at the hands of Chelsea, Liverpool and Tottenham Hotspur, some fans had suggested that Alan Curbishley should change his telephone number to Upton Park 040404, but super sub Sears pressed all the right buttons and made an instant connection.
With Luis Boa Morte suspended following his reckless red card in the third of those lamentable losses at White Hart Lane last Sunday, the Hammers made just one change as Nolberto Solano returned to the starting line-up.
Blackburn - without a win at Upton Park in a dozen previous visits dating back to April 1994 - made three changes in response to last weekend's 1-1 draw with Fulham as Tugay and substitutes Benni McCarthy and Zurab Khizanishvili made way for Brett Emerton, David Dunn and Jason Roberts.
And it was Rovers that showed all the early initiative as Morten Gamst Pedersen sent an awkward corner across the face of goal, while Santa Cruz headed Emerton's cross wide and Christopher Samba nodded onto the roof of Robert Green's goal.
In truth, the confidence-sapped Hammers were offering minimal threat and, with David Bentley running the show on his return to the capital, they were made to pay on 19 minutes.
The England midfielder intercepted the ball from Scott Parker and picked out the escaping Pedersen, whose left-flank centre found the unmarked, diving Santa Cruz who headed a sweet 16th goal of the campaign beyond the unprotected Green.
West Ham finally awoke from their slumber as Parker drilled a 20-yarder just wide before Ashton saw Brad Friedel palm his well-placed header around the post and the tireless Solano had a long-range free-kick guided over.
The shoots of recovery were there and, on 39 minutes, Green booted a free-kick upfield towards the head of Bobby Zamora, who nodded the ball into the path of Ashton.
After turning Samba, the top-scoring Hammers striker clipped an angled 12-yarder over the advancing Friedel to net his seventh goal of the season.
Buoyed by their equaliser, West Ham emerged for the restart in determined mood and, after Zamora had unleashed a low, angled 15-yarder across the face of goal, Friedel denied Ashton a second with a full-length save.
In reply, Pedersen wastefully launched the ball high over with the goal at his mercy before Hughes introduced Matt Derbyshire in place of Dunn.
But with ten minutes remaining, it was Curbishley's double introduction of Mark Noble and Sears that was destined to have the more dramatic impact.
Indeed, within just five frenetic minutes of his arrival, supporting super sub Sears entered East End legend, when he raced onto Ashton's clever back-heel and unleashed a low shot that Friedel could only palm skywards.
And with the Rovers keeper groping the Upton Park turf, the diving teenager hurled himself at the looping ball to give West Ham victory with a dream debut goal.