Two goals in each half helped United to a comfortable victory over Cardiff City in the Welsh capital on Monday evening.
Che Adams, who completed 45 minutes on his return following illness, opened the scoring, before a Paul Coutts, who enjoyed his first action since the end of last season, doubled the advantage before the break from the penalty spot.
In the second-half skipper Terry Kennedy headed home a third, before substitute Jamie McDonagh rounded off the scoring in stoppage-time.
The opening exchanges of the game saw little in the way of goalmouth action, with both teams looking to get a foothold in the contest.
In the 15th minute John forced Long into an excellent save from a free-kick, whilst at the other end Adams fizzed over a set-piece for the Blades.
Just before the half hour O'Keefe volleyed over and O'Sullivan drove an effort inches wide, before United made the home side pay at the other end.
The lively ADAMS capitalised on a defensive slip to fire home past the Wilson in the Bluebirds goal and moments later COUTTS made it two from the spot after McFadzean had been fouled by Tamas.
Before the break, City should have reduce the arrears, Long did well to initially deny Kennedy, and the United stopper was quickly back on his feet to deny Abbotts on the rebound.
The first meaningful action of the second period saw Wilson deny McFadzean, before Khan replaced Scougall and that substitution was followed by the introduction of Whiteman.
Blaise and Kennedy had chances for the hosts, before United made it three in the 77th minute, with KENNEDY rising highest to head home.
And the visitors weren't finished there, as MCDONAGH raced clear in the final moments of the game to get his name on the scoresheet and United's fourth at the Cardiff City Stadium.
The win is United's second consecutive away success, after Diego De Girolamo brace helped defeat Watford at Vicarage Road earlier this month.
Blades: Long, Phillips, K. Wallace, Dimaio, Kennedy, McGahey, Scougall (Khan 59) Coutts, Adams (McDonagh 45), De Girolamo, McFadzean (Whiteman 63).
Unused: Eastwood, Evans.