Sitting in eighth and fifth position respectively in the Eredivisie, both clubs know that this competition represents their only chance of earning silverware during the 2020-21 campaign.
There was a time earlier in the season when Feyenoord were in contention to challenge for the Eredivisie title as they kept pace with Ajax and PSV Eindhoven.
However, three defeats in four league matches have left Dick Advocaat's side down in fifth position, 12 points off the pace.
While finishing in the top five is still the bare minimum expected, Advocaat will be eyeing this trophy with Ajax and PSV squaring off in one of the other last-eight ties.
The veteran manager will be optimistic that a place in the last four can be achieved after witnessing his Feyenoord side outplay PSV at the weekend, eventually prevailing by a 3-1 scoreline.
That performance was in stark contrast to the display which was produced in the previous game against Heerenveen, their next opponents winning 3-0 without breaking much of a sweat.
The home side will have taken the positives from the manner of that success, although Johnny Jansen will stress to his players that they cannot get carried away by their recent form.
Although seven points have been claimed from three games against teams sitting above them in the table, De Superfriezen still sit nine points adrift of fifth spot.
Heerenveen have reached this stage of the competition with wins over TOP Oss and Emmen, while Feyenoord edged past mid-table FC Utrecht.
Heerenveen KNVB Beker form: WW
Heerenveen form (all competitions): DWLWDW
Feyenoord KNVB Beker form: W
Feyenoord form (all competitions): WLWLLW
Despite Sunday's important fixture with AZ, Jansen could name his strongest XI for this contest.
With Feyenoord having not played since the win over PSV at the end of January, Advocaat may stick with the team which won that match.
Nicolai Jorgensen is expected to remain among the substitutes after the front three all contributed in that previous fixture.
Heerenveen possible starting lineup:
Mulder; Hecke, Dresevic, Bochniewicz, Kaib; Kongolo, Halilovic, J.Veerman; De Jong; Bergen, H.Veerman
Feyenoord possible starting lineup:
Marsman; Geertruida, Botteghin, Senesi, Malacia; Toornstra, Fer, Diemers; Berghuis, Linssen, Haps
We say: Heerenveen 1-2 Feyenoord
Heerenveen will be confident of recording another eye-catching win after their recent resurgence in the Dutch top flight. However, Feyenoord looked back on track against PSV, and we feel that Advocaat's side will edge a competitive encounter on Thursday night.