Union could end up in the relegation spots, retain their playoff place or avoid the drop against Christian Streich's side, who aim to clinch a continental place in the departing manager's final game.
Match preview
Union were 45 minutes away from a first Bundesliga victory since mid-March after racing to a two-goal lead against second-bottom Koln. However, the Iron Ones collapsed in Cologne to lose 3-2, leaving them in a precarious position heading into the final day.
Marco Grote was placed in charge of the capital club for the second time this season after Nenad Bjelica's exit at the start of May, and the interim boss hopes for a final push against Freiburg in gameweek 34.
The previous round's results saw Mainz leapfrog the Berlin-based club after dispatching Champions League finalists Borussia Dortmund 3-0, and Koln's turnaround against Grote's side leaves Die Eisemen also looking over their shoulder to avoid falling into the automatic relegation spots.
Supporters heading to the Forsterei on Saturday will hope for maximum points to end a run of three straight defeats on their turf, keen to give themselves a chance of keeping their top-flight status.
Defeat for Union (30 points, -26 goal difference) and a win for Koln (27 points, -29 goal difference) at Heidenheim could see the Iron Ones end second-bottom. Conversely, victory for the capital club and a Mainz (32 points, -14 goal difference) loss at Wolfsburg would see gameweek 34 conclude with the club staying up.
Despite the home side's ambition, Freiburg have theirs to end Streich's time at the club with a win, possibly guaranteeing European football for the Black Forest side.
Eighth could secure Conference League football for the Breisgau Brazilians if Bayer Leverkusen defeat Kaiserslautern in the DFB-Pokal final — meaning the seventh-placed then get Europa League football.
However, Streich hopes to leapfrog Hoffenheim — who host Bayern Munich — into seventh on the final day, keen to end his 12-year spell at the club on a high, and that remains a possibility if the Black Forest side win on Saturday and Bayern defeat Die Kraichgauer.
The travelling fans have reason to be optimistic, having gone over two months without an away defeat since losing 2-1 at Augsburg in late February. That run stands at stands at three wins and a draw, with Freiburg keeping clean sheets in victories over Borussia Monchengladbach (3-0), Darmstadt (1-0) and Koln (0-0).
Freiburg should be placed higher in the standings if their results at the Europa-Park Stadion were satisfactory but they did not win any of their final eight games on home turf. Having recently relied on their road results, the Breisgau Brazilians hope for one last triumph to end the outgoing manager's time with maximum points.
Union Berlin Bundesliga form:
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L
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D
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L
Freiburg Bundesliga form:
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W
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D
Team News
Rani Khedira was booked in Union's last match with Koln, thus ruling out the midfield man on Saturday.
A knock means Kevin Vogt is doubtful for the Iron Ones, but Jakob Busk (calf) is not expected to feature on the final day.
Kiliann Sildillia is still suspended after his sending-off against Wolfsburg at the backend of April (gameweek 31).
Streich has to deal with several absentees, with Matthias Ginter (Achilles), Manuel Gulde (hamstring), Daniel-Kofi Kyereh (knee), Philipp Lienhart (knee), Merlin Rohl (thigh) and Kenneth Schmidt (abdominal) all missing this weekend.
Ritsu Doan netted in Freiburg's wins at Gladbach and Darmstadt, and the wing-back could impact Saturday's game down the right side again.
Union Berlin possible starting lineup:
Ronnow; Doekhi, Knoche, Leite; Trimmel, Haberer, Schafer, Roussillon; Aaronson, Volland, Gosens
Freiburg possible starting lineup:
Atubolu; Kubler, Keitel, Makengo; Doan, Eggestein, Hofler, Gunter; Sallai, Gregoritsch, Grifo
We say: Union Berlin 1-2 Freiburg
It is hard to look beyond a win for Freiburg on Saturday, despite Union's dire need for one. The departing Streich has seen his side thrive on the road in recent weeks, an antithesis of their wretched home form, and they should inflict a fourth straight loss on the Iron Ones on Saturday.