Featuring in eight matches in the Primeira Liga so far, the 21-year-old is already supposedly attracting interest from La Liga sides Real Madrid and Barcelona.
Fernandez has also shone on the continental stage, earning rave reviews for his performance during Benfica's 4-0 thrashing of Atletico Madrid in the Champions League.
The left-back started his senior career on loan at Preston North End in the Championship from Man United, making 42 appearances across all competitions for the second-tier outfit.
Earning seven caps for Spain Under-21s since his debut in September 2023, Fernandez also possesses relative international pedigree at a young age.
Man United 'have two years' to trigger buy-back clause
According to the Manchester Evening News, Man United are not in a rush to use the buy-back clause present in Fernandez's Benfica deal despite his stellar displays so far this season.
The report claims that the Red Devils have until the summer of 2026 to trigger the option, should they wish to bring the defender back to Old Trafford.
It is understood that Man United have placed similar clauses in outgoing deals for other players who have departed the Theatre of Dreams.
Benfica secured the services of full-back Fernandez for around £5m near the start of the summer transfer window ahead of the 2024-25 campaign.
It is believed that there are no imminent plans for the Red Devils to trigger the option, but the Premier League strugglers are aware of the Spaniard's positive start to life in Portugal.
Could Fernandez end Man United's left-back woes?
Despite Fernandez playing for Man United through the age groups up to the Under-23s, he was unable to earn a first-team appearance before a sale to Benfica in the summer.
The 21-year-old could have provided a natural option at left-back for the Red Devils, who have suffered serious fitness issues in that position over the past 18 months.
England international Luke Shaw has not featured for Man United since a Premier League trip to Luton Town in February due to numerous injury setbacks.
Since making the high-profile switch from Feyenoord to Old Trafford in July 2022, Tyrell Malacia has only played 39 matches for Erik ten Hag's troops.