Paris Saint-Germain will offer £41.5million for the Brazilian in the summer but they are not the only club to be keeping tabs on the 22-year-old.
If Barcelona and Monaco spark a bidding war by tabling their own offers, however, the sum may increase to somewhere nearer the £50m mark.
All three clubs are expected to spend heavily at the end of the season with all interested in the South American, tipped to be one of the stars of the forthcoming World Cup.
The playmaker was signed from Internacional for £25m in July 2012 and Blues boss José Mourinho is likely to be reluctant to let him leave.
