Sevilla have concerns about Gonzalo Montiel's form with Nottingham Forest.
The defender is on-loan at Forest with a purchase option included.
Estadio Deportivo says Montiel can sign permanently with Forest for 11m, which will be obligatory if he plays 50 per cent of games.
Sevilla are "keeping an eye" on the situation, though Montiel's injury problems are creating concern.
The LaLiga club hope to sell Montiel next summer.