Both clubs are currently competing for silverware in their respective leagues, leaving it open to interpretation whether this competition is a distraction at this stage of the season.
Match preview
Having posted four draws in five league fixtures, Ajax dropped off the pace in the Dutch top flight, but the introduction of Johnny Heitinga has instigated a change in fortunes.
Since stepping up from Ajax's second-string, the former defender has recorded four victories in succession, with 13 goals being netted during those quartet of fixtures.
Although Ajax have faced no team higher than fifth-placed FC Twente, a fixture which came in the KNVB Beker, it has been a necessary resurgence if they want to win any silverware this campaign.
Even with three league wins in a row, Ajax still sit three points adrift of leaders Feyenoord, who have dropped four points over the same period.
Ajax spent the first half of the season competing in the Champions League, finishing in third spot in a group which also featured Napoli and Ajax.
As far as Union Berlin are concerned, they put together a bizarre run of results in their Europa League games, each of those fixtures ending 1-0.
After losing the first two matches to Union SG and Braga, the German outfit recorded four wins with that particular scoreline in their favour, two of the triumphs coming versus Malmo.
Urs Fischer will have ambitions to go as far as possible in this competition, but he will also have one eye on ensuring that his team do not lose any momentum in the Bundesliga.
In recent seasons, Union Berlin have gone from surprise packages to title contenders, the Iron Ones currently sitting just one point adrift of dominant champions Bayern Munich.
Five victories have been posted in a row, the most recent coming at the home ground of in-form RB Leipzig last time out.
Ajax form (all competitions):
D
D
W
W
W
W
Union Berlin Europa League form:
L
L
W
W
W
W
Union Berlin form (all competitions):
W
W
W
W
W
W
Team News
Heitinga may choose to keep changes to a minimum for this fixture, potentially making just one alteration to bring Brian Brobbey back into the team.
That would likely see Francisco Conceicao drop out with Dusan Tadic moving out wide to feature on the left flank.
Although Calvin Bassey is an option in the defence, the former Rangers man may have to make do with a spot among the replacements.
Fischer will be forced into making at least one change to his Union Berlin XI with Janik Haberer serving a one-match ban for three yellow cards.
Either Morten Thorsby or Paul Seguin are in line to be handed a recall, but further rotation is a possibility with Timo Baumgartl, Jerome Roussillon and Jordan Siebatcheu all options in defence, on the flank and in attack.
Christopher Trimmel is also suspended for Union Berlin, although he was only named on the substitutes' bench at the weekend.
Ajax possible starting lineup:
Rulli; Rensch, Alvarez, Timber, Wijndal; Berghuis, Taylor, Klaassen; Kudus, Brobbery, Tadic
Union Berlin possible starting lineup:
Ronnow; Doekhi, Knoche, Leite; Juranovic, Laidouni, Khedira, Thorsby, Roussillon; Becker, Behrens
We say: Ajax 1-1 Union Berlin
With both clubs in a period of strong form, this can only be a highly-competitive contest. There will be a desire to remain in the tie ahead of the second leg in Germany, and we would not be surprised to see a share of the spoils play out in Amsterdam.