Mata at the double in United win
The 25-year-old Spaniard struck twice to take his tally to three goals in his last two games and pay off another slice of his £37.1million transfer fee.
On a day when manager David Moyes was without the injured Wayne Rooney, and decided to make eight changes to the side which drew 1-1 with Bayern Munich in midweek ahead of Wednesday night's return leg, United ran out deserved winners as the Magpies' early promise dissolved.
The win was not without controversy, with referee Kevin Friend - the official who had to deal with Alan Pardew's head-butt on Hull's David Meyler - coming under fire for awarding the free-kick from which Mata gave United a first-half lead.
However, there were no complaints thereafter as Mata extended the lead five minutes after the break and further strikes from Javier Hernandez and substitute Adnan Januzaj wrapped up the victory.
The defeat was Newcastle's fourth in five league games, a run which has seen them score just one goal, and in truth there was little prospect of them completing a first league double over United since 1931 from the moment that Mata struck.
There was an end-of-season feel about the game before kick-off, with Moyes keeping one eye on Munich and opposite number Pardew missing five of the men who started the 1-0 win at Old Trafford in December.
As a result, there was inevitably a makeshift look about both sides with United patient in their build-up, in which a deep-sitting Marouane Fellaini figured prominently, as they tried to find space for Hernandez and Mata.
Newcastle's approach was more direct with Davide Santon, lining up at right-back rather than on the left, making life difficult for Patrice Evra to supply a series of dangerous crosses.
It was he who produced the second-minute ball from which Dan Gosling, making his first Barclays Premier League start for the Magpies since December 2011, headed just wide, and he who picked out striker Papiss Cisse to force a fine 24th-minute save from Anders Lindegaard with a glancing header.
But, too often, the home side squandered possession in promising positions to let the visitors off the hook.
Moyes' men lost winger Ashley Young with a dislocated finger after just 18 minutes and home keeper Rob Elliot had little to do for much of the first half.
However, the game turned six minutes before the break and it did so in controversial circumstances.
Gosling was furious to be penalised for a trip on Darren Fletcher on the edge of the box, but as the home fans made their feelings known to Friend, Mata stepped up to curl a delicious left-foot free-kick high into the top corner with Elliot powerless to resist.
The game could have been effectively over in the final minute of the half when, after Friend had allowed play to continue with central defender Mike Williamson appealing for a foul by Hernandez, the Mexican ran on to Shinji Kagawa's through-ball to shoot past Elliot, only to see the ball come back off the foot of the post.
However, any hopes of a fightback were dealt a fatal blow within five minutes of the restart and this time Newcastle had no-one to blame but themselves.
Skipper Fabricio Coloccini's ambitious attempt to chest a long ball to full-back Massadio Haidara fell short and Kagawa stole in to pick out Hernandez's run.
The striker fed Mata inside the box and he cleverly side-stepped Coloccini's desperate lunge before slotting calmly into the bottom corner.
Hernandez might have made it 3-0 with a snapshot which flew over on the hour, and it was then that the Magpies opted for change with Hatem Ben Arfa replacing the ineffectual Luuk De Jong.
But Hernandez made amends with 25 minutes remaining when he slid home from close range after Januzaj and Kagawa teamed up to play him in.
Lindegaard had to turn away Cisse's curling 71st-minute effort and then produced a remarkable stop to deny the same man from just six yards before Mata set up Januzaj to complete the rout with an audacious back-heeled pass.
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