In the context of the FIFA Ultimate Team (FUT) game mode in FIFA video games, loan players can sometimes be used in Squad Building Challenges (SBCs), but it depends on the specific SBC requirements.
Some SBCs may allow you to use loan players as part of the squad building requirements, while others may require only untradeable or non-loan player cards. Additionally, some SBCs may have specific requirements, such as a minimum overall rating or team chemistry, which may make it difficult or impossible to use loan players.
It's always a good idea to carefully review the SBC requirements before attempting to complete it and to consider all available player options, including loan players, when building your squad.
