Manchester United suffered one of the most humiliating defeats in their long and proud history as MK Dons piled yet more misery on Louis van Gaal.

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The new United boss, now without a win in three matches, watched on in misery as his team were knocked out of the Capital One Cup at the second-round stage with a 4-0 defeat.

Will Grigg and Arsenal loanee Benik Afobe scored a brace apiece as United were easily downed by a team that began the night 38 places below them in the league ladder.

It was a hugely embarrassing defeat -- one that brought back unwanted memories of their last League Cup second-round fixture in 1995 when they lost to York.

But it was nothing more than the Red Devils deserved.

A team showing 10 changes from the 1-1 draw at Sunderland never settled all night.

Fringe players like Danny Welbeck, Javier Hernandez, Shinji Kagawa and Anderson were given chances to fight for a place in the first team.

But they all under-performed. Until the dying stages, when the Dons' victory had already been assured, home goalkeeper David Martin had very little to do.

United handed the victory to the League One side on a plate thanks to a shabby defensive performance.

Jonny Evans, captain for the night, made a glaring error to hand the Dons the lead and from then on it never looked like the underdogs were going to lose.

Van Gaal may have Angel di Maria to count on to aid his recovery -- the 59.7 million pound signing was confirmed just before kick-off -- and on this evidence, many more replacements are needed, particularly at the back.

The 26,969 fans inside stadium:mk did their best to make United feel unwelcome as they took to the pitch, but in the early stages it appeared to have little effect as the Premier League club started well.

With 50 seconds on the clock, Welbeck raced down the wing and found Hernandez at the back post, but the Mexican slipped just as he was about to pull the trigger.

Nick Powell then fired a 25-yard shot just over the bar.

Hernandez punctured the Dons defence with a burst of pace, but he was pulled back for tugging Antony Kay's shirt.

Welbeck also broke through the back line in the ninth minute, but he could not test Martin.

From then on, the United team, which contained two debutants, went to pieces.

David de Gea had to race off his line to deny Grigg, who had given Reece James the slip to latch on to Darren Potter's headed through-ball.

Van Gaal was forced into a change when Kagawa was replaced by Adnan Januzaj following a clash of heads with a Dons defender.

Then came the moment Evans will not forget in a hurry.

The centre-half, under no pressure whatsoever, passed straight into the path of Ben Reeves inside the United box. The former Southampton player kept his cool and squared to Grigg, who slotted the ball past De Gea.

Evans held his head in his hands while the home fans taunted Van Gaal with chants of ``You're getting sacked in the morning''.

There was no immediate response from United. In fact, they were happy to go in at the break just one goal down.

Even the simplest of passes seemed beyond the 20-time English champions.

Hernandez, Anderson and Powell were all guilty of wasteful play and Martin had nothing to do in the home goal.

Mamik Vermijl's clearance landed straight at the feet of Samir Carruthers, but he shot straight at De Gea.

Van Gaal replaced the poor Saidy Janko with another debutant, Andreas Pereira.

The League One side continued to hold their own after the restart and they thought they should have had a penalty when Dean Bowditch's shot struck Evans' arm. Stuart Attwell waved play on.

Welbeck offered a glimpse of the quality United needed with a fizzing shot that flew just wide.

Defensive vulnerabilities cost United again though as the Dons stunned the home crowd with a second goal.

Evans played a careless ball to Michael Keane, who had little time to clear. The hosts took advantage down the right through Reeves, who whipped in a flat cross which Grigg flicked past De Gea with his chest.

It was an audacious finish that would not have looked out of place at the Nou Camp, rather than the Moo Camp -- the local name for stadium:mk due to the presence of the concrete cows nearby.

Seven minutes later a third flew in. Baldock gained some space down the left and found Reeves. He played the ball in behind to Afobe, who rifled past De Gea.

The home fans could not believe the scoreline. There was time for more excitement though. Afobe showed the fight United lacked, driving past three defenders before beating De Gea.

Martin pulled off a string of top saves to keep a clean sheet and put the icing on a miserable night for Van Gaal.