The veteran midfielder picked up a groin injury in the first leg of their tie against Heerenveen and could miss the return fixture as well as the next round.

Siem de Jong replaced Davids shortly before half time.

"Edgar felt something snap near his groin and at the bottom of his belly," Koster told local channel AT5.

"He felt pain in his groin and he will go later on Friday to a hospital. Hopefully it will not be that bad."

Ajax play the return leg against Heerenveen on Monday in the ArenA.

The capital club take a 2-1 lead into the tie and they will be hoping to make it to the second and final round of the play-offs.