The Bluebirds have never won their opening three league games and tonight, against Neil Warnock's hometown club, they get a rare chance to make a bit of history.
The Blades are new to the division after several years in league One and have started with a win and a defeat in their opening two games.
Cardiff are one of four sides with a 100% record so far, with Wolves, Forest and Ipswich the other three.
Sky Sports preview:
Sky Bet Championship leaders Cardiff will make it three league wins out of three if they see off one of manager Neil Warnock's former clubs on Tuesday.
Despite an impressive 3-0 victory over Aston Villa, Warnock could decide to make changes for Sheffield United's visit to Wales as he utilises a powerful-looking squad. Striker Lee Tomlin, who was among the substitutes against Villa, might be in line for a start, and Warnock is also likely to consider a full Cardiff debut for £1.6million signing Danny Ward.
Bruno Manga, meanwhile, is another player set to be debated, with Warnock possibly giving him a run instead of Sol Bamba prior to next Saturday's Molineux appointment with unbeaten Wolves.
Sheffield United boss Chris Wilder has no new injuries as his side look to bounce back from their first defeat since January. The Blades' 20-game unbeaten run was ended at Middlesbrough on Saturday, but Wilder picked up no fresh concerns.
The boss has hinted he might change things around in Wales, though confirmed Ched Evans will not start. George Baldock is also a little way off a return while goalkeeper Simon Moore is recovering from a knee operation.
Opta stats:
Cardiff have only managed a victory in one of their last five Championship home games against the Blades (D2 L2), with the last two contests ending 1-1.
However, the Welsh outfit have only lost one of their last eight league encounters against Sheffield United (W3 D4).
Neil Warnock is set to meet his former club Sheffield United for the eight time since he left them in 2007; he's lost only one of those seven meetings (W3 D3), a 2-0 defeat as Crystal Palace manager in December 2009.
Cardiff have won both of their opening two games to a league season for the first time since 2011-12 - the Bluebirds have never won their first three games of a league season in their entire history.
Billy Sharp has scored just 12 goals in his 61 Championship appearances since the start of 2013-14 - this compared to 51 goals in 90 League One appearances over the last two seasons.
Match Officials:
Referee: LEE MASON
Assistants: Jake Collin and Dan Cook
Fourth Official: Andy Davies