The 27-year-old Brazilian has reportedly been watched for a number of weeks by Kenny Dalglish's scouts but now face rivals for his signature.
Serie A outfit Napoli are thought to be one of the sides interested in signing the former FC Zurich player, and Raffael's agent Dino Lamberti says the race is hotting up.
Lamberti told Tutto Mercato: "At the moment, Napoli have not specifically asked for him, but I can say that he is wanted by several Italian clubs.
"The amount needed is €15m (£12.4m)."
Raffael looks set to leave the German capital as Hertha languish second from bottom in the Bundesliga.