Vitesse Arnhem consolidated its bid for a place in the end-of-season UEFA Europa League qualifying play-offs with a comfortable 3-1 win at relegation-threatened VVV-Venlo.
ADO Den Haag moved seven points clear of the Eredivisie relegation zone with a 3-0 win over Groningen.
Rydell Poepon opened the scoring in the 22nd minute and De Leeuw sealed the win with goals in the 62nd and 88th minutes.
De Graafschap's win leaves Excelsior bottom of the table and in the automatic relegation place, with De Graafschap and VVV-Venlo in the relegation play-off places.
Celtic is moving closer to agreeing a deal to sign Netherlands Under-21 defender Virgil van Dijk.