#4 Robert Lewandowski
The Bayern Munich striker has been on and off Chelsea's radar, with Manchester United also long-term admirers. Having made a name for himself as one of Europe's most deadly strikers, the Poland international will not come cheap should he angle for a move away.
However, it's becoming increasingly clear that the Blues need a forward with a proven track record - having seen Álvaro Morata struggle to adjust to the Premier League's physicality and intensity in recent months. The Spaniard could still turn things around and the presence of a more experienced attacker like Robert would certainly have a positive impact on his development going forward.
At 29-years-old, it's now or never. Lewandowski himself has said recently that he's happy at Bayern, but things can change quickly in football and he could be persuaded into a new challenge in a different league, should Chelsea's interest be genuine.
That being said, only a significant transfer fee will manage to convince Bayern into parting ways with their prized asset.