Benfica head coach Roger Schmidt is not sure if Friday's 3-0 loss to Braga was Enzo Fernandez's last for the club amid reports that he has agreed to join Chelsea.
Fernandez starred for Argentina during their triumphant World Cup campaign, prompting speculation of a move during the January transfer window.
The 21-year-old, who joined Benfica from River Plate last year, was rewarded for his efforts by being named as the Young Player of the Tournament.
Reports on Friday claimed Fernandez had already agreed to join the Blues, with the ball now in Benfica's court as to whether they accept a bid.
"I don't know if it was his last game for Benfica," Schmidt told reporters. "He's an excellent player, he's been performing fantastically, he's identified with the club.
"Sometimes things happen and players have to make decisions. We'll see what happens in the coming weeks."
Schmidt opted to start Fernandez along with Nicolas Otamendi in Friday's game despite their short break after their World Cup triumph.
"Nico and Enzo were good today," he added. "They were at their normal level. As I said before the game, they came with rhythm, they were always playing.
"Others were at the World Cup, didn't play, didn't train much. They need some time to get back to their best form. Overall we weren't good enough. You can't change."