Sky Sports sources understands Chelsea have agreed a deal to sign Metalist Kharkiv midfielder Taison, but face competition for his signature from another Premier League club.
Taison revealed earlier this month that he had spoken to Chelsea about a possible move to the club after making a visit to West London.
The Brazilian joined Metalist two-and-a-half years ago from Internacional, where he played with current Chelsea midfielder Oscar.
Metalist are reluctant to lose the attacking midfielder, but Chelsea are believed to have agreed a fee with the Ukrainian side and have agreed personal terms with Taison.
However, an unnamed Premier League club is also thought to have made an approach to Metalist for Taison and are ready to rival Chelsea for his signature.
Chelsea remain favourites to land Taison and are hopeful of pushing through a deal to make him their second signing of this month's transfer window following the capture of Demba Ba.