After their 3-1 Premier League victory over Crystal Palace on Saturday, Allardyce outlined his intention to field a much-changed side when the London club host Nigel Clough's League One side in the second round on Tuesday.
With top flight survival so crucial to West Ham, the visit of the Yorkshire club will allow the 59-year-old to ring the changes and allow some of his players yet to feature in the league some time on the pitch.
That could mean first starts for new signings Enner Valencia and Diafra Sako, while Ravel Morrison is likely to feature after returning from his loan spell at QPR last season.
Allardyce has the option of recalling centre-back James Collins after the defender sat out the victory at Selhurst Park due to a one-match suspension.
West Ham reached the semi-finals of the competition last year and while another long run in the competition would swell the coffers, Allardyce is not prepared to risk seeing his injury list lengthen.
"I have alluded to the fact that I've already got five players injured and I am not going to risk too many on Tuesday because Southampton is just round the corner," he told Sky Sports.
"If pick up injuries I weaken the team, we have enough to play an experienced team with a couple of young players, only a couple.
"I can blood Sako, Valencia, get Ravel [Morrison] back, Mo Diame in there, Diego Poyet, Guy Demel and Jussi Jasskelainen.
"That's the kind of side I'm going to pick with a couple of young ones in. I think that is the right thing to do for us all, think that team are capable of beating Sheffield United if they approach the game in the right manner."
The clash sees two sides come together for the first time since the final compensation payment was made by West Ham to the League One club over the third-party ownership affair involving Carlos Tevez.
West Ham, who were found guilty of breaching Premier League rules, agreed a deal with their opponents after Tevez, who was deemed ineligible to play by an independent tribunal, scored a crucial goal to keep them in the top flight and relegate United on the final day of the 2006/2007 season.
They reached the semi-final of the FA Cup last season, but have not fared well in this competition, having suffered four exits in the first round in the last five seasons.
Clough's side should not be taken lightly, though, given they come into the game on the back of successive wins in the league.
