Transfer expert Fabrizio Romano confirmed City's interest, describing the 16-year-old as "an interesting profile" with at least one other Premier League club and Bundesliga giants also in the mix.
The queue is growing fast.
Arsenal, Manchester United, Bayern Munich, Real Madrid and Barcelona have all been linked with Eichhorn in recent months. Arsenal sporting director Andrea Berta has reportedly held direct discussions with his camp. United see him as a long-term replacement for Casemiro. Real Madrid's scouts believe he could be a future successor to Toni Kroos at the Bernabéu.
The Kroos comparison has been circulating since Eichhorn broke into Hertha's first team last August — becoming the youngest player ever to start a Bundesliga 2 match in the process, at 16 years and 14 days old.
Hertha coach Stefan Leitl had no hesitation throwing him in.
After Eichhorn's debut, Leitl described him as "by far the best player on the pitch."
The boy from Bernau, just north-east of Berlin, has made 15 appearances across all competitions this season, scoring his first professional goal in a DFB-Pokal win over Kaiserslautern. He captains the Germany Under-17 national team.
His game draws comparisons to Kroos for a reason. He scans constantly, receives on the half-turn, distributes over short and long distances and appears entirely unaffected by the occasion. Veteran Hertha defender Toni Leistner put it simply: "What the lad can do is astonishing."
The release clause in his contract stands at €10-12 million — a figure that will become active this summer and is the reason elite clubs are moving now rather than later.
Eichhorn is currently recovering from an ankle injury, but a summer departure is widely expected.
At €12 million for a player of this potential, every club in Europe has a reason to call.