United exited the Carabao Cup at the second-round stage after being defeated on penalties by Burnley following a 1-1 draw at Turf Moor.
In a tight encounter, David McGoldrick had given United the advantage early on before Matej Vydra's second-half equaliser took the game to penalties. Oli McBurnie's miss proved crucial as Burnley netted all five spot kicks as the home side advanced into round three where they will face Millwall.
Boss Chris Wilder gave five players their full Blades debut with Wes Foderingham, Jayden Bogle, Max Lowe, Ethan Ampadu and Oli Burke all starting. Ollie Norwood was the only figure in the 11 who started Monday's season curtain raiser against Wolves, as the Blades boss handed opportunities to a host of players.
United made a lightning start to the game and had the lead after just four minutes. The Blades were quickly into their stride and after some neat build up play involving Norwood and Sander Berge, the latter slid a ball in behind for the onrushing Lowe. The former Derby ace quickly got his head up to slide a low cross into the path of McGOLDRICK who had the simple task of converting from close range.
The Blades pinned the hosts back in the opening stages as Wilder's side quickly found a rhythm. An early Norwood corner was cleared with United playing some crisp high-tempo football from the loose ball as Bogle combined well with Ben Osborn, before an offside flag curtailed a promising move.
Burnley were forced into the first change as Johann Berg Gudmundsson went off injured after a challenge from Jack Robinson, with Erik Pieters coming on in his place.
There were plenty of attacking positives for United in the opening 30 minutes with both Bogle and Lowe keen to get forward on debut. The latter burst into the Burnley area on 27 minutes with a surging run, but his cross was too close to Nick Pope.
The Burnley 'keeper was called into action again on 31 minutes when Norwood's dangerous delivery arrowed under his crossbar forcing the England stopper to claw the ball clear. The Blades played some great football at times with Berge dropping a sublime pass in behind for Burke whose touch almost worked a shooting chance for Lowe.
Burnley gradually pulled themselves back into the contest and United were lucky just before the break when Vydra was sent clear on goal. The onrushing Foderingham appeared to bring down the striker for a certain penalty but United were saved by the offside flag.
The hosts began the second half on the front foot and should have been level on 51 minutes. Some quick first time passing allowed the Clarets to counter attack with Pieters surging deep into United territory. The sub played a perfect pass for Robbie Brady who was clean through on goal, but his low shot saw a fine touch off Foderingham before cannoning off the post.
United responded instantly and created a half chance when Norwood's through ball found McGoldrick on the angle, but his low shot was blocked by Jimmy Dunne.
Wilder freshened up his front-line just after the hour with McBurnie and Billy Sharp replacing Burke and McGoldrick.
Burnley grew in confidence as the half wore on and levelled on 67 minutes. After the Blades dealt with a Burnley corner, the danger seemed to have been averted. Then a long ball forward was eventually seized upon by Jay Rodriguez who laid the ball into the path of VYDRA inside the area who converted beyond the advancing Foderingham.
The Blades hit back on 72 minutes with the impressive Lowe causing problems. His low cross stuck at the feet of Sharp but as he created the half yard needed to shoot his effort was smothered by a Burnley defender.
United were now in the ascendency with Norwood seeing a low strike saved after good work by Berge. With 12 minutes remaining McBurnie had a shot deflected into the side netting after a low cross from Lowe, whilst the hosts got lucky soon after when Kevin Long fluffed a clearance from Bogle's cross but the ball fell kindly for the home side.
Late on McBurnie thought he'd won it when Norwood's corner was cleared before being fired back into the mix where the striker turned a low shot towards goal only to be denied by the feet of Pope.
The match went straight to penalties and it was McBurnie who was denied by a low save by Pope again, with Burnley netted all five penalties to advance.
Burnley: Pope, Lowton, Long, Dunne, Taylor, Westwood (Benson 76'), Brownhill, Gudmundsson (Pieters 14'), Brady, Vydra, Rodriguez (Wood 81').
Unused: Peacock-Farrell, Thomas, Bardsley, McNeil.
Blades: Foderingham, Berge, Lowe, Burke (Sharp 62'), Jagielka, Norwood, McGoldrick (Sharp 62'), Robinson, Bogle (Basham 87'), Ampadu, Osborn.
Unused: Ramsdale, Slater, Bryan, Brunt.
Burnley: Wood (scored), Vydra (scored), Brownhill (scored), Pieters (scored), Brady(scored).
Blades: Norwood (scored), McBurnie (saved), Sharp (scored), Berge (scored), Osborn (scored).
As it happened...
It is United to kick-off and we're underway.
First free-kick to Burnley as Sander Berge brings down Vydra on halfway.
The ball is hoisted forward but Brady's cross is cleared at the near post.
United ahead with the first attack!
Lovely build up play as Berge finds Norwood. He slides a ball in behind for wing-back Lowe and his cross is turned in by David McGoldrick.
Half chance for Rodriguez who blazes over from a tight angle as Burnley respond positively from the restart.
United really looking in the mood in the opening stages.
A Norwood corner is cleared and then some lovely play is halted by the offside flag as Bogle combined with Osborn.
Burnley have had to make a sub here as Pieters replaces Gudmundsson.
Dangerous cross from the right as Lowton looks to pick out Vydra. Jagielka got the last touch as he forces it behind.
Long wins the header from the resulting corner but the whistle has been blown and it's a free-kick to United.
Good spell for Burnley as they enjoy more of the ball over the last five minutes.
Brady delivers a deep cross which is just too strong for Vydra lurking at the far stick.
Max Lowe showing signs of intent again as he bursts into the Burnley area but his cross is too close to the 'keeper who makes a routine claim.
Almost a chance for Rodriguez.
Robinson's clearance is blocked and kindly falls for Lowton but the low cross just eludes the striker.
United free-kick as Osborn is caught late.
Norwood delivers right under the crossbar forcing Pope to claw the ball clear under pressure.
Some great football by United.
Berge with an inventive ball over the top into the area. There's a touch by Burke into the path of Lowe but as he waits for the ball to drop to shoot he is smothered by the Burnley defence.
United saved there!
Vydra sent clear, he gets to the ball just ahead of Foderingham who brings him down. It looked a certain penalty but the flag had already been raised for offside.
Let off for the Blades.
Good work again by United as Bogle feeds McGoldrick into the channel.
He weaves inside and out before drilling a low cross into the area which is cleared by Long with pink shirts lurking.
Three added minutes.
Burnley 0 - 1 Blades
David McGoldrick's early goal has United in front at half-time.
Burnley to kick-off and we're back underway...
Quiet start to the second half. Nothing really to report as Pieters' long ball forward is headed into the arms of Foderingham.
Big let off for United!
Swift Burnley counter as Pieters darts forward. He slides Brady clean through on goal but his low shot canons off the post to safety.
United respond. Berge with the break before slipping a pass to Norwood, he plays in McGoldrick but his low shot on the angle is blocked by Dunne.
Soon after the same player hooks a shot over after a knockdown from Robinson. Better from United.
The second half has hit a stalemate here but United won't mind.
The Blades still lead and Foderingham untroubled since the Brady effort off the post.
Double change for United.
Goalscorer McGoldrick and Oli Burke replaced by Billy Sharp and Oli McBurnie.
Burnley are level. United clear a Clarets corner but the home side come again after a long pass. Rodriguez then chests a ball into the path of Vydra who converts. 1-1.
Jagielka into the book after bringing down Vydra on the edge of the area.
Brady's free-kick then hits the wall and diverts behind for a corner.
Westwood's delivery is dealt with. Home side on top though.
United back on the attack.
Lowe again causing a threat going forward. His cross sticks at the feet of Sharp six yards out, he creates the shooting opportunity but a wonderful last ditch block denies the skipper.
Brady smashes a ball forward which almost gets Rodriguez in behind but it is a poor touch from the striker and the ball runs clear.
Patient build up play again from United as Berge just inside the area with his back to goal, lays off to Norwood whose crisp low strike from 25 yards is held by Pope.
Benson replaces Westwood for Burnley.
Absolute peach of a cross from ex-Blade Lowton but Vydra can't get the right connection and glances a header wide.
It's Lowe again causing problems for the Burnley defence.
Tidy cross into McBurnie who takes a touch 18 yards out but a good effort is deflected into the side-netting.
Nothing comes from the corner but United getting stronger.
A reminder this will go straight to penalties if it stays level.
Foul on Vydra by Ampadu and it is a yellow card for the Chelsea loanee.
Rodriguez is replaced by Chris Wood.
Luck for Burnley as Bogle's cross causes a problem.
Long completely fluffs a clearance but no-one in pink there to take advantage.
Bogle is replaced by Chris Basham.
Late corner for United won by Lowe.
Norwood's cross is just over the head of Robinson. The ball is returned and McBurnie stabs a shot towards goal but Pope makes a great save with his legs.
Three added minutes.
Burnley 1 - 1 Blades
McGoldrick's early strike is cancelled out by Vydra in the second half.
We go to penalties!
United up first....
It's Ollie Norwood...
Right footed, converts, sends Pope the wrong way.
Wood for Burnley...
Blasts it past Foderingham. He didn't mess about there! 1-1.
Saved low down by Pope! 1-1.
Smashes it past Foderingham. 2-1 Burnley.
Scores!!! Just! Pope got a hand to it, but it goes in. 2-2.
Scores. Foderigham went early, the wrong way. 3-2 Burnley.
Coolly done. Sends Pope the wrong way. 3-3.
Left-footed, plants it into the corner, Foderingham goes the wrong way. 4-3.
Osborn must score...
Brilliant pen, smashed into the roof of the net. 4-4.
Brady to win it...
Slots it into the bottom corner! Foderingham goes the wrong way. Burnley win the shootout 5-4 and advance into the next round.