Kovačić suffered a serious injury in 2009 in which his leg was broken, but he returned to the pitch after a lengthy recovery on 31 May 2010, appearing in the last match of the Croatian under-17 academy league, a 5–0 win against RNK Split under-17s.
Kovacic mengalami cedera serius pada tahun 2009 di mana kakinya patah, tetapi ia kembali ke lapangan setelah pemulihan yang panjang pada tanggal 31 Mei 2010, muncul dalam pertandingan terakhir dari Kroasia U17 akademi liga, kemenangan 5-0 melawan U17s di Split RNK .