Two goals, two red cards and around five late saves from Brentford goalkeeper Daniel Bentley were the highlights of the Good Friday trip to Griffin Park.
Chris Basham netted and Jamal Blackman was sent off.
Basham, who missed the last game due to the birth of his child, returned to the starting line-up and Lundstram was also recalled. They took over from Duffy, who missed out with a groin problem, and Lee Evans, who was only deemed fit enough for the bench after extensive travelling whilst on international duty with Wales.
Persistent rain throughout the build-up and the game was a significant factor and possibly one of the reasons why neither side could gain control early on. The first work for either goalkeeper arrived on 13 minutes when Blackman pushed away a 20-yard effort from
Neat work around the Bees box from Baldock, Clarke, Lundstram and Fleck could not open up the home side, who looked a threat when Yennaris sliced wide and Maupay tried to poke home ahead of Blackman but the Blades goalkeeper smothered.
The first United chance, on 20 minutes, saw Sharp off target and the Blades skipper was offside when Baldock delivered soon after.
Goalkeepers Blackman and Bentley saved from Mepham and Fleck respectively and United forced another chance on 39 minutes but a goal-line melee resulted in referee Simpson finding a free-kick to the defending side.
The final chance of the half, in injury-time, saw Bentley fluff a punch but Baldock returned the ball wide of the uprights.
The early stages of the second half were uneventful, prompting boss Wilder to make his first change, Evans for Lundstram, and within minutes United were in front.
Brentford only half-cleared a corner and after Fleck ran at the defence, the ball broke to BASHAM to fire home, possibly with the aid of a deflection.
Donaldson took over from Sharp just after the hour and with the rain continuing, the pace increased ahead of a spot of drama.
MEPHAM levelled for Brentford following recycled ball from a set-piece and as he set off to celebrate, home midfielder Woods and Blackman were involved in a spat on the goal-line. The incident happened right in front of the Bees fans and as they made their voices heard, referee Simpson showed both players his red card. Before play could restart, Leonard was sacrificed for Moore to take his place in goal.
The final 20 minutes saw both sides going for the victory but Bentley was clearly the busier of the two goalkeepers. He was off his line quickly to deny Donaldson and then the stopper was well placed to hold another Basham shot.
On 86 minutes, there was a great opportunity as Clarke beat two defenders but Bentley was brave to save and then Fleck lost his marker but saw a right-foot effort blocked.
The only chance of note in five minutes of added time saw Bentley again thwart United at the death, denying Donaldson.
Brentford: Bentley, MacLeod (Mokotjo 60), Jozefzoon (Judge 78), Yennaris, Maupay, Egan, Woods, Clarke, Dalsgaard, Mepham, Canos (Watkins 60).
Unused: McEachran, Marcondes, Daniels, Barbet.
Blades: Blackman, Baldock, Stevens, Fleck, O'Connell, Basham, Lundstram (L Evans 52), Clarke, Sharp (Donaldson 63), Leonard (Moore 71), Stearman.
Unused: Wilson, Lafferty, Holmes, Brooks.