The 20-year-old has made the breakthrough into the Barcelona first team during the 2023-24 campaign after an impressive loan spell with Linares in Spain's third tier last term.
Fermin has been a regular for Xavi's side this season, featuring on 33 occasions in all competitions, contributing six goals and one assist in the process.
The Spaniard has scored three times in 23 La Liga matches this term, while he has also managed two goals and one assist in seven Champions League fixtures.
Fermin signed a new deal with Barcelona last August, with his current terms due to run until June 2027, but there is currently speculation surrounding his long-term future at Camp Nou.
The youngster has benefitted from midfield absences this season, and he is likely to find it difficult to secure regular starts when Gavi, Pedri and Frenkie de Jong are all available for selection.
According to Fichajes, Leverkusen are huge admirers of Fermin, and the German club's head coach Xabi Alonso has identified him as a leading target for the summer market.
The report claims that the Bundesliga team want to take advantage of Barcelona's financial situation in order to secure the midfielder's signature in the upcoming market.
Leverkusen allegedly believe that a fee of around €20m (£17m) could be agreed, and Fermin would be offered a starting role at BayArena.
Can Barcelona afford to let Fermin leave?
Fermin has proven to be a vital player for Barcelona this season considering the team's injury problems in midfield, and he has shown that he has the quality to operate at the top level.
When Barcelona have a full squad available, he is unlikely to be in the XI, with De Jong, Gavi, Pedri and Ilkay Gundogan all ahead of him in the pecking order when it comes to the midfield spots.
However, Oriol Romeu is likely to leave this summer, and with Marc Casado not yet being trusted to feature on a regular basis, it would be a surprise to see Fermin depart.
Barcelona are under pressure to make some first-team sales in the upcoming market, especially as they want to keep hold of on-loan duo Joao Felix and Joao Cancelo.
There are other players who could be sold for higher fees, though, and it is unlikely to be a worthwhile deal for Barcelona at €20m (£17m) considering his potential.