If certain players cannot agree on a new contract with their current clubs, then they will be able to sign pre-contract agreements with other teams this month.
It means that when their deals expire at the end of this season they can join another side for nothing.
Here, talkSPORT.com looks at a starting XI of the most expensive players currently in the last year of their contracts.
All values are courtesy of transfermarkt.com.
Remain up to date with all transfer stories this month right here.