Borussia Dortmund face a gap at the heart of their defence following Niklas Sule's retirement and a serious knee injury to captain Emre Can, who suffered a cruciate ligament tear.
The club are looking for a robust central defender with the pace and passing range to fit their system, and according to German outlet Fussballtransfers, they believe they have found that profile in Fernandez.
Dortmund are not alone in their interest. According to the Daily Record, Bayer Leverkusen have also shown significant interest in the 24-year-old Nigeria international.
Both Bundesliga clubs were already tracking Fernandez during the January transfer window, and reports suggest a string of impressive performances since then has only strengthened their conviction.
Fernandez joined Rangers from English third-tier side Peterborough United last summer for a fee of around €3 million, and has since become an undisputed starter at Ibrox.
Standing at 1.98 metres and born in London, the defender has impressed with his physical duels, reading of the game and strength in the air.
He has also shown a goal threat from set pieces, scoring five times in 22 league appearances this season.
Fernandez's rise has been remarkable given his footballing background. He only made his senior breakthrough at Peterborough last season before Rangers paid roughly £3.5 million to bring him to Scotland.
Since the arrival of head coach Danny Rohl in October, Fernandez has been a near-constant presence in the Rangers backline, and he was named in the PFA Scotland Premiership Team of the Year for his performances this season.
His form has also earned him a first call-up to the Nigeria national team, where he made an immediate impact on his debut.
Beyond Dortmund and Bayer Leverkusen, reports throughout the season have linked Fernandez with Arsenal, Chelsea and Everton in the Premier League, as well as Club Brugge, Ajax and Feyenoord.
Fernandez is under contract with Rangers until 2029, with the Scottish club holding an option for a further year, giving them control over the timing of any sale.
Given the fee Rangers paid for him just twelve months ago, any departure this summer looks set to represent a substantial financial windfall for the Scottish club, with Peterborough also due a portion of any future transfer fee as part of their sell-on agreement.