The 20-year-old signed for the Blues in July for a reported fee of around £8 million from Dutch outfit Vitesse, but Ajax tried to bring the midfielder in on loan before the summer transfer window closed.
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"He made no mistake, because he really wanted to come to Ajax, but Chelsea did not let him," Overmars told De Telegraaf.
With competition for places so fierce at Chelsea, Overmars has no doubt it would have been beneficial for the young midfielder to remain in his homeland.
"Would it have been better for his development to go to Ajax? Yes, 1000 per cent," he added.
"We tried to get him on loan in this transfer window but unfortunately Chelsea would not let him go."
Van Ginkel, who has been likened to Frank Lampard, has made two substitute appearances in the Premier League so far this season.