Frenkie de Jong could miss Tuesday's Champions League clash against Juventus after suffering an injury in Ajax's 6-2 win over Excelsior.
Coach Erik ten Hag said it was too early to say whether De Jong would miss the quarter-final second leg in Turin, where Ajax will be on the backfoot after a 1-1 draw in last Wednesday's first leg.
De Jong, who moves to Barcelona at the end of the season, had an impressive showing in last week's clash in Amsterdam.
But he was withdrawn after just 22 minutes on Saturday clutching at his hamstring.
Frenkie de Jong shows he and Barcelona can be a match made in heaven
"He felt something wrong with his hamstring and so we took him off as a precaution," Ten Hag said. "We were already 1-0 up so there was no point taking any risks."
De Jong had also been injured the match before the first leg but played a full 90 minutes against Juventus last Wednesday.
Saturday's victory for Ajax put them three points clear of PSV Eindhoven at the top of the standings with PSV in action at home on Sunday against struggling De Graafschap.
