The pair’s goals came either side of Dennis Praet’s strike to ensure a positive end to United’s summer and gave them a boost ahead of next Tuesday’s European Super Cup clash with Real Madrid in Macedonia.
United boss Jose Mourinho gave new £40million signing Nemanja Matic his debut and the former Chelsea man strolled through a comfortable 45 minutes before being replaced by Michael Carrick at the break.
The Italians, 10th in Serie A last season, had no shots on target in the first half, and the closest they came to a goal was from a Danny Blind backpass that required a full length save from David De Gea.
De Gea’s handling of the ball gave the Italians an indirect free kick on the edge of the six yard box, but United’s defenders blocked and immediately countered.
Antonio Valencia stormed clear on the right wing and fed Mkhitaryan, who then found Matteo Darmian on the left wing. His cross back into the box was headed home by Mkhitaryan to turn Sampdoria’s opportunity into a United goal in just 30 seconds.
Valencia and Mkhitaryan teamed up again two minutes later with the winger nipping past his opposite number, before whipping in a cross that veteran keeper Christian Puggioni did well to punch clear from Mkhitaryan’s header.
The right wing proved a fertile ground for United, with Romelu Lukaku sent clear moments later. The Belgium international cut inside smartly but pushed his left foot strike narrowly wide.
Sampdoria came within inches of an equaliser just before the break, and once more it was down to a United mistake with Daniel Pavlovic’s free kick bouncing off Victor Lindelof’s thigh and going narrowly wide of De Gea’s post.
The English side made four changes at the break, and two of them, Marouane Fellaini and Ander Herrera combined to put the ball in the net on the hour, but the Spaniard’s strike was disallowed for offside.
Out of the blue, Sampdoria equalised on 63 minutes, with Praet calmly finishing from the edge of the box, after a poorly cleared cross fell his way. It was the Italian team’s first shot on target.
The Serie A side grew into the game, but United had the last laugh, with two more replacements, Mata and Anthony Martial teaming up to see the Spaniard grab a deserved winner in the 81st minute.
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