Despite spending big last summer on several players, including Moises Caicedo, the Blues have had a disappointing start to their season.
Their forwards, in particular, have struggled, with Senegalese striker Nicolas Jackson failing to impress despite scoring seven Premier League goals.
Christopher Nkunku is also out with a hip injury, with a return date unknown as the club attempts to inject attacking vigour this month.
Who is Mateo Cassierra?
With 14 goals in the Russian Premier League campaign, Cassierra has managed to attract interest from a number of European sides.
The 26-year-old is known for his heading ability and physical presence inside the box which is exactly what Chelsea need.
In addition to his scoring prowess, the forward also excels in link-up play and has an eye for a pass having provided five assists in all competitions this season.
He is currently Zenit’s top scorer and should Chelsea make an approach to sign the player on a permanent deal, the Colombian would cost them a fee estimated to be in the region of £10 million.
