A very shaky defence has been just one of the startling features of this season's poor United side, and with Nemanja Vidic on his way out of Old Trafford in the summer, reinforcements are needed.
It also seems likely that Rio Ferdinand will retire at the end of the season, and with Chris Smalling and Phil Jones not wholly convincing, Garay's quality would be hugely beneficial at the back.
And there is certainly interest from David Moyes and the powers that be at Old Trafford.
Manchester United and Chelsea sent scouts to Benfica's Stadium of Light on Thursday night to watch defender Ezequiel Garay.
The 27-year-old Argentine scored the opening goal as Benfica beat Spurs on aggregate to reach the Europa League quarter-finals.
His central defensive partnership at the other end of the field, however - with Brazilian Luisao - has been pivotal as the club close in on the Portuguese title.
United are long-term admirers of Garay, but the Argentine blamed last summer's instability for his Old Trafford move falling through and there is now likely to be a summer battle for the player who is open to a move to the Premier League.
United will certainly face competition for his signature, but they must try to bring him in, because a stronger defence would be a perfect platform on which to build a better side.
Benfica currently sit seven points clear at the top of the Portuguese league and have conceded only 15 goals in 23 games this season.
The Old Trafford side will not be able to compete with the best again until they shore things up at the back.
Garay has proven he can play at the top level with Benfica and in his 18 senior caps for Argentina, including nine caps in their World Cup qualifying campaign, per Goal.com.
As well as his solidity defensively, the 27-year-old is more than adequate going forward and has contributed nine goals in his 73 league appearances for Benfica, per soccerbase.com.
Benfica centre back Ezequiel Garay has scored Benfica's three last goals in all competitions. Goalgetter.— Jan Hagen (@PortuBall) March 20, 2014
Although United could conceivably rely on Smalling, Jones and Jonny Evans to take up the centre-back mantle next season, this would be a dangerous plan.
While all are potentially high-quality players, they have yet to prove it on a regular basis. Garay could be a terrific influence and partner for these players at Old Trafford.
They cannot afford to miss out again.