CIES (The International Centre for Sports Studies) Football Observatory Weekly Post ranks countries worldwide according to the number of their representatives having played professional football abroad during the calendar year 2019. 

Croatia is in the top ten, or more precisely at nineth place with 446 players who are abroad, of which 71.5 percent is in top division.

Brazil is at the top of the table (1,600 players, of which 74.6 percentactive in top division leagues) ahead of France (1,027, 74.0 percent) and Argentina (972, 75.5 percent).

In total, 186 national associations had at least one player expatriated in the 141 leagues from 93 countries included in the sample. However, altogether, Brazil, France and Argentina provided up to almost one quarter of the total foreign workforce in global football (22.5 percent). Nigeria is the main African exporting nation (399 players abroad), while Japan is the principal Asian one (161).

You can see the full list here.