In the 37th minute of the traditionally intense Eredivisie clash on Sunday, defender Janmaat and winger Wesley Verhoek corralled Ajax's Ryan Babel in the corner.

As Babel won a throw in, Janmaat was hit in the head by a bottle and fell to the ground but was able to play on.

The 23-year-old Dutch defender suffered no serious consequences.

The bottle was thrown from within the Feyenoord supporters end of their home ground, De Kuip, in Rotterdam.