The Iron Ores went down 2-0 to Borussia Dortmund as goals from Marco Reus and Raphael Guerreiro in either half ended their three-game unbeaten run.
The loss kept Urs Fischer's side four points off sixth-placed Bayer Leverkusen in the race for the Europa Conference League play-off spot with just four games remaining in the season.
Werder Bremen are looking to snap a six-game losing streak right now, having gone completely off the boil since beating Arminia Bielefeld in March.
They have landed themselves back in a relegation scramble and hover just four points above the bottom three.
Union Berlin vs Werder Bremen Head-To-Head
There have been five previous meetings between the sides, with the spoils being equally shared at two wins each.
However, the Iron Ones have beaten Bremen in each of their last two clashes, including a 2-0 victory in January.
Union Berlin Form Guide (all competitions): L-D-D-W-L
Werder Bremen Form Guide (all competitions): L-W-L-L-L
Union Berlin vs Werder Bremen Team News
The capital side will be without Anthony Ujah (knee surgery), Taiwo Awoniyi (torn muscle), Leon Dajaku (foot) and Sheraldo Becker (ankle surgery), but there are no fresh injury concerns for Fischer.
Niko Gießelmann returned to the bench last time out but remained an unused substitute. He'll be pushing for a start in this game.
Injured: Anthony Ujah, Taiwo Awoniyi, Leon Dajaku, and Sheraldo Becker
Omer Toprak, Luca Plogmann, Nick Woltemade and Niclas Fullkrug will remain sidelined, while Leonardo Bittencourt will be out until mid-May with an injury to his ankle, sustained in the game against Borussia Dortmund last week.
Milos Veljkovic suffered a broken nose in the last game and will be out too.
Injured: Milos Veljkovic, Omer Toprak, Leonardo Bittencourt, Luca Plogmann, Nick Woltemade and Niclas Fullkrug
Union Berlin vs Werder Bremen Predicted XI
Union Berlin (4-4-2): Loris Karius; Christopher Trimmel, Marvin Friedrich, Robin Knoche, Christopher Lenz; Grischa Promel, Robert Andrich; Marcus Ingvartsen, Keita Endo; Max Kruse, Petar Musa.
Werder Bremen (3-4-1-2): Jiri Pavlenka; Patrick Erras, Niklas Moisander, Marco Friedl; Theodor Gebre Selassie, Maximilian Eggestein, Kevin Mohwald, Ludwig Augustinsson; Romano Schmid; Milot Rashica, Josh Sargent.
Union Berlin vs Werder Bremen Prediction
The River Islanders are currently stuck in a rut and Berlin have the tools to compound their misery on Saturday.
Prediction: Union Berlin 2-1 Werder Bremen