Phil Jagielka's 57th-minute header may have wiped out Marlon Harewood's excellent first-half opener to secure a deserved rematch, but on an afternoon short on football and long on feistiness there was little else to warm the crowd.
Both sides had seen off Premiership opposition in the third round, the Blades having cut down Aston Villa while the Hammers had knocked the Canaries of Norwich City off their perches.
West Ham brought back Teddy Sheringham, Steve Bywater, Anton Ferdinand and Mark Noble following last weekend's defeat against Derby County, while Nick Montgomery was the only Sheffield United change from the team that had gone down at Sunderland.
But Championship standings were to count for nothing in this tightly fought contest where goal opportunities were few and far between.
Indeed, the first real chance of the match did not arrive until the quarter-hour mark when Paddy Kenny found Harewood's scorching 20-yarder too hot to handle but with no-one following up, the danger was cleared.
Ten minutes later, it was Sheffield United's chance to threaten and this time Michael Tonge let fly with an 18-yard shot that crashed off Bywater's left-hand post.
Just as a frustrating first half looked set to end goalless, though, Harewood – scorer of the third-round winner against Norwich - raced on to Sheringham's 39th-minute throughball.
But just he looked set to tumble under pressure from his marker, the falling Hammers striker somehow kept just enough balance to hook a 15-yard shot over the advancing Kenny to claim an innovative 14th goal of the season.
Having edged the first half, West Ham's interval cuppa would have tasted that much sweeter, but the break also gave Neil Warnock time to rally his troops.
Sure enough, as the hour mark approached, the Blades levelled when Andy Liddell carved his way down the left and centred for Jagielka to send his downward header over the line as Bywater vainly tried to scoop the ball back into play.
Referee Dermot Gallagher was having none of it, though and bookings for Carl Fletcher, Tomas Repka and Noble soon followed as the frustrated Hammers struggled to come to terms with the fact that they had so meekly surrendered their advantage.
Nigel Reo-Coker and Sergei Rebrov - who was also subsequently cautioned- were introduced late on, but there was nothing that the substitutes could do to prevent Hammers from having to endure that Bramall Lane replay.