Complex sentence: However under Ronald Koeman, caretaker Martin Haar and Dick Advocaat, he was rarely played and made only 11 substitute appearances, but under Gertjan Verbeek he would become a regular player.
Split into simpler sentences: However under Ronald Koeman, caretaker Martin Haar and Dick Advocaat, he barely got any playing time, as he only made 11 substitute appearances. But under Gertjan Verbeek, he would become a regular player.