Reports earlier this month suggested United were keen on Garay amidst concerns over the long-term fitness of Rio Ferdinand and Nemanja Vidic.
Record report that representatives from Manchester United were present to watch Garay in Benfica's 2-0 win over Pacos de Ferreira last night in which the Argentinian international made his return from a shoulder injury.
The paper reports that the Red Devils went as far as to make a bid for the 26-year-old, but were knocked back after Benfica deemed it to be insufficient. Scouts from Chievo were also casting an eye over the defender.
With time fast running out, a summer move for the Argentinian international seems most likely.
Red Devils boss Sir Alex Ferguson remains adamant that there will be no new arrivals in the January transfer window, although a deal has already been agreed for Crystal Palace's Wilfried Zaha to head to Old Trafford in the summer.