Portuguese giants Benfica have slapped a £20million price tag on Manchester United target Nemanja Matic. Serbian midfielder Matic had two years at Chelsea early in his career but never started a match for them and spent the second season on loan at Vitesse Arnhem. But the 25-year-old has blossomed in Lisbon after joining in summer 2011 as part of the deal that took David Luiz to Stamford Bridge, Matic has been watched by United scouts in his last two games and the Old Trafford giants have stepped up their interest. Champions United are desperate to strengthen their midfield in January but could face competition from Italians Napoli.