Ajax midfielder Frenkie de Jong left Saturday's game against Excelsior injured and there are fears he could miss the game against Juventus on Tuesday.
Ten Hag's side have just three days before their Champions League quarterfinal second leg in Turin -- the first leg ended 1-1 in Amsterdam.
De Jong has to be rated as a major doubt for that fixture after being taken off in the 24th minute clutching the back of his leg. He headed straight to the dressing room.
Ajax went on to win the game to keep their hopes of winning the league title alive but now face an anxious wait to see how De Jong recovered.
Remember he was also a doubt for the first leg against Juve with an ankle problem but was fine to take his place in the XI in the end.
De Jong will move to Barcelona at the end of the season. The Catalan side will pay an initial 75 million euros for the Dutch international.