According to the Daily Mirror, Chelsea officials watched Garay in action against Tottenham in the Europa League. And they will no doubt have left impressed after another composed display by the United target at the heart of the Benfica defence.
Alongside centre-back partner Luisao, the 27-year-old Argentina international remained solid in defence and chipped in with his team's first goal. Benfica beat Spurs on aggregate to advance to the Europa League last eight.
Long linked with Manchester United, it was even reported at one stage that United had clinched a deal with Benfica to bring him to Old Trafford.
But that never materialised, and Zenit St Petersburg were also heavily linked with the defender in the winter transfer window.
But now Chelsea have also joined the race to sign the talented centre-back, with the future of club captain John Terry still uncertain.
The Stamford Bridge legend has been in talks over a new Chelsea contract, but is yet to agree a deal and could still depart at the end of the season.
That would force Jose Mourinho into the transfer market to sign a replacement, and Garay, who has been valued at £8m in the past, would represent good value for money when compared to alternatives, chiefly Porto's Eliaquim Mangala.