Quite simply, Dean Ashton could not have left it any later to break plucky Plymouth Argyle's hearts.
The in-form striker struck his killer 92nd-minute winner to put Hammers into the Carling Cup fourth round and send the Pilgrims marching home defeated but with their heads held high.
And on a damp East End night, Ashton's third goal in successive games - a timely 101st strike of his career - proved the clinical difference between the two sides in this end to end encounter.
Insisting that West Ham United are capable of progressing to the latter stages of the Carling Cup, Alan Curbishley still named a strong, solid side, despite making half-a-dozen changes from the team that had lost its second game of the season at Newcastle United on Sunday afternoon.
Indeed, fit-again Scott Parker was handed a welcome debut in a Hammers' midfield that also included Freddie Ljungberg and Luis Boa Morte, while Richard Wright took over in goal behind the Welsh defensive duo of James Collins and Danny Gabbidon.
And although that meant there were no places for Anton Ferdinand, Matthew Upson and Matthew Etherington, Curbs was taking no chances as he placed Robert Green, Mark Noble and Lee Bowyer on the bench alongside Jonathan Spector and Kyel Reid.
Argyle had only suffered their second defeat of the present term at the weekend, too, and Ian Holloway made just two switches from the side that lost at Stoke City, as he recalled top-scoring, five-goal Sylvain Ebanks-Blake and veteran Barry Hayles at the expense of Nick Chadwick and Rory Fallon.
Sitting in 13th-spot in the Championship, Argyle had already seen off Wycombe Wanderers and Doncaster Rovers in the competition but they arrived at Upton Park facing a much sterner test against a Hammers side, which having beaten Bristol Rovers in the second round, also sat 26 league rungs above them.
Undaunted, the men from the West Country confidently set about taking the game to their hosts and Ebanks-Blake and Hayles were soon extending Curbs' defence across every blade of their sodden Upton Park penalty area.
And with West Ham being forced to rely on sporadic early breaks, Boa Morte called Luke McCormick into a low save with a 20-yard shot, before Peter Halmosi nodded Collins' powerful 15th-minute header out from under the left-hand angle.
In reply, the energetic Ebanks-Blake then sent a rising 15-yarder sizzling over the top and, as Plymouth continued to threaten, Akos Buzsaky landed a long-ranger on the top of Wright's net before Krisztian Timar headed over.
Gathering momentum, West Ham had their chances to break the deadlock in an intriguing first-half, too.
After Ashton sent a low 18-yard shot aqua-planing just an agonising inch or so past the base of McCormick's right-hand post, the escaping Boa Morte then looked odds-on to break the deadlock on 34 minutes when he skipped clear, but the Portuguese winger scooped his effort wide of both the Argyle 'keeper and his left upright.
And five minutes before the interval, Ashton then saw his subtle, side-footer palmed aside at full stretch by McCormick, before Lucas Neill also ensured that it remained goalless at the break, when he chested Halmosi's dipping 18-yard free-kick off the line.
Ashton emerged for the restart sporting the red boots that had seen him net his first goal in 490 days against Middlesbrough on his last home outing, and he soon sent a powerful header over the top before creating a few scares in the Pilgrims' danger zone.
With Collins and Gabbidon still being occupied by the probing Plymouth strike-pairing, Curbs shuffled the pack with the introduction of Reid at the expense of Carlton Cole and, after the Hammers' youngster had a 20-yarder deflected for a corner, both Boa Morte and Timar followed Gabbidon into referee Phil Dowd's book for feisty tackles.
Bowyer then replaced Ljungberg and, as the game entered the final quarter-hour, both sides were going all out to avoid an unwelcome bout of extra-time.
Only a double goal-line block by Wright and then the covering Neill denied Hayles six yards out, while at the other end Ashton's ambitious 25-yard free-kick looped up off the Plymouth wall onto the roof of McCormick's net.
Then, in the dying seconds of normal time, Bowyer's downward header bounced wide to the frustration of the drenched Hammers' fans amongst the 25,774 crowd.
But seconds later, that despair turned to delight, when Reid's inch-perfect, deep cross to back of the Plymouth area picked out those red boots of Ashton, who clinically despatched an angled 12-yarder into the far corner to finally break that Argyle resistance.