After a much-needed 3-1 victory over relegation rivals Luton Town at Kenilworth Road during the previous weekend, the Blades came nowhere near sealing back-to-back wins for the first time this season last time out.
Mason Holgate's horror tackle - and subsequent dismissal - set the tone for a difficult afternoon at Bramall Lane for Chris Wilder's side, who conceded five times in a match for a second-straight home fixture.
Argentina's Facundo Buonanotte opened the scoring for the visiting Seagulls before Danny Welbeck fired Brighton into a two-goal lead at the interval, giving the Blades a mountain to climb in the second period.
Fighting on wounded and with a numerical disadvantage, Wes Foderingham's net was breached a further three times in the second half, with Jack Robinson scoring an own goal and Simon Adingra bagging a brace.
Following a five-star showing from Roberto De Zebri's men in South Yorkshire, Sheffield United have now let in 65 goals during their opening 25 Premier League matches, setting a new record.
The second-leakiest defence at this stage of a Premier League campaign belongs to Barnsley's class of 1997-18, who conceded 61 goals in the same number of top-flight clashes.
Unsurprisingly, the Tykes were relegated to the Championship after finishing 19th at the end of that particular campaign - a fate that Wilder's Blades appear to be destined to also.
Sheffield United have now conceded 36 goals in their first 13 matches, with only two sides in English top-flight history possessing a poorer defensive record over that period of matches.
Darwen finished bottom of a 14-team first division in 1891-92 after conceding an eye-watering 43 goals in their opening 13 home league clashes.
A more familiar name takes the unwanted silver medal in this particular statistic, with Aston Villa's 1935-36 side letting in 41 goals during 13 matches in front of their own supporters.
Replacing Paul Heckingbottom as the Blades head coach in the middle of the season, Wilder looked to immediately improve his defensive department in January, recruiting Ivo Grbic from Atletico Madrid to become United's new first-choice goalkeeper.
After making his Premier League debut in the loss to Crystal Palace on January 30, the Croatian stopper suffered a concussion and has not featured competitively since.