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.
He was taken off after just 22 minutes of Ajax’s 6-2 win over Excelsior clutching at his hamstring.
“He felt something wrong with his hamstring and so we took him off as a precaution,” Ten Hag told reporters afterwards. “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, although PSV play at home on Sunday against struggling De Graafschap.