1)ARSENAL- DIEGO COSTA
Current club: Atletico Madrid
Estimated transfer fee: £32 million ($66.9m)
The over-reliance on striker Olivier Giroud may return to haunt Arsenal, who headed into the new year as Premiership leaders.
The Gunners will certainly run into trouble should the Frenchman go down with injury, as the cover looks wafer-thin.
Nicklas Bendtner looks incapable of leading the frontline, and while Lukas Podolski can play as a striker, manager Arsene Wenger prefers to stick him out wide.
Diego Costa is in the form of his life at Atletico Madrid, who are level on points with Barcelona at the top of the Spanish La Liga table.
The Brazilian's 19 league goals in 17 matches, which put him top of the scorers' chart, is the main reason for that.