Despite a struggling first half performance on 28th December (at Bramall Lane) the Blades came out in the second half; Danny Webber ruled out Hameur Bouazza's first half strike, whilst two goals from Stephen Quinn sealed the victory.
The Blades booked a place in round four following a 4-1 victory at Brisbane Road - the original fixture was postponed due to a frozen pitch but the game went underway a week last Tuesday. Again a sluggish first half ended in the opposition ahead at the break, JJ Meligan firing home from the spot after Matthew Kilgallon was deemed to have hand balled.
In the second half things were different with Greg Halford looping home for the equaliser, Billy Sharp and Kyle Naughton made the game safe before Halford headed home at the far post to seal a place in round four.
Blades boss Kevin Blackwell will be without midfielder Gary Speed (back) and defender Ugo Ehiogu (Achilles) who are both out for the remainder of the season.
New signing Jamie Ward, a £330,000 capture from League Two outfit Chesterfield will not be allowed to make his debut against Athletic, the 21 year old striker is cup tied after featuring in the Spirites cup run against Mansfield Town, Droylsden and Ipswich Town.
Leigh Bromby, who re-signed for the Blades last week will sit this match out - the former Sheffield Wednesday and Norwich City Defender is cup tied having featured in the Hornets 1-0 victory over Scunthorpe United in round three - he played just one minute after replacing Tamas Priskin in the 89th minute to defend their lead.
Winger Keith Gillespie may feature against former club Charlton Athletic, he spent a month on loan at the Valley before being recalled this season - the Northern Ireland international made four (+2) appearances for the Valley club during his one month loan spell. He is likely to win a placer on the substitutes bench.
Meanwhile Greg Halford is expected to feature against the rival Championship side; he spent four months on loan at the Valley during the 2007-08 campaign, making 16 (+0) league appearances and netting twice.
Possible Blades Line-Up: Ian Bennett; Sun Jihai, Kyle Walker, Chris Morgan, Matthew Kilgallon, Greg Halford, Kyle Naughton, Brian Howard, Stephen Quinn, Darius Henderson, Billy Sharp.
Charlton Athletic won a place in round four after seeing off Championship rivals Norwich City, it took a replay but the London club won for the first time in 18 league and cup fixtures to set a tie up with the winners between Orient and United.
In late November 2008 United recorded a 5-2 victory in London with goals from; James Beattie, Gary Speed, Matthew Kilgallon, Kelly Youga (own goal) and Stephen Quinn with replies from Linvoy Primus and Hameur Bouazza for the Addicks - no doubt the Bramall Lane faithful wish to repeat that great performance.
The club could however turn to former Blade strikers Andy Gray and Izale McLeod with the latter likely to miss out. Gray became a signing from Bradford City in February 2004 and became an instant hit, netting on his debut at Reading in a 2-1 defeat.
He transferred to Premier League outfit Sunderland in a £1,100,000 deal following a clause in his contact in August 2005 having made 63 (+2) appearances, whilst scoring 28 goals. Meanwhile Izale McLeod arrived at Bramall Lane on loan from Derby County in March 2004 until May, he made just one (+6) appearances - the Blades opted out of an option to buy the forward and he joined MK Dons (then Wimbledon) instead.
Matthew Spring, a recent addition to the Athletic side spent the first half of the season on loan to the Blades from Luton Town, he made just 10 (+3) appearances whilst netting once in a 3-1 home defeat to Wolverhampton Wanderers. Although on a seasons long loan from Kenilworth Road he left the Blades in January to team up with Phil Parkinson.
Possible Athletic Line-Up: Darren Randolph, Mark Hudson, Jonathan Fortune, Grant Bassey, Yassin Moutaouaki, Scott Wagstaff, Nicky Bailey, Josh Wright, Darren Ambrose, Lloyd Sam, Deon Burton.