The 25-year-old spent two years at Chelsea before joining Benfica, but did not start a game for the Blues.
Matic has become a key player at Benfica since joining in the summer of 2011.
The Mirror reports that Matic has been watched by United scouts in his last two games.
United could make a move for Matic in January, but face competition from Italian giants Napoli.
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Liverpool have unveiled their new home kit for next season, sticking with the hugely popular retro styling of the current shirt.
The reputation of the Premier League means it is the most popular and one of the most watched leagues in the world.