Nicolas Otamendi asked Valencia to be excused from training as he is 'not in the right frame of mind', according to reports in Spain.
The Argentina centre-back has been linked with a move to Manchester United all summer, with neighbours Manchester City also said to have entered the race in the last week.
Otamendi, 27, only joined the club last summer but was extremely impressive for Los Che, scoring six goals on the way to helping the club reach the Champions League.
The defender, who helped Argentina reach the final of the Copa America in the summer, is said to have a €50million (approx. £35m) release clause.
According to Spanish newspapers AS and Cope, Otamendi asked manager Nuno to be left out of training because his 'mind, at this time, is elsewhere'.
Manchester United are reported to be unwilling to pay the full release clause and want to negotiate a smaller feeReuse content