Answer
Saúl Ñíguez was loaned to Rayo Vallecano for the 2013–14 season. This was a decision made by Atlético Madrid in order to give the young player more playing time and experience. Ñíguez had been with Atlético since he was a child and had come through the club's youth academy. He had made his first-team debut in the 2012–13 season, but he had not played regularly.