Many FIFA 15 players find a new direction for their career during the winter transfers window. In order to keep the game updated, EA release new cards to these players in their new clubs. The first batch of new cards was released at January 20th. The main one will be released at February 1st.
The new cards allow you to build more teams with good chemistry. These cards replace the old ones into packs. The cards with the old clubs are not updated and are no longer released in packs. That is, the same player can have cards from two different clubs at the same time but can be found in packs only with the new club.