Eighth in the standings with 31 points from 21 games, the Breisgau-Brasilianer are just two worse off than Borussia Dortmund and Borussia Monchengladbach. A playoff spot in the Europa Conference League is within sight.
They've won seven of their last 11 league games, losing only twice. That run has propelled them into the top half of the table after a stuttering first few months.
Meanwhile, Berlin have had a stop-start season but have done enough to remain inside the top 10.
They have secured victories against heavyweights such as Borussia Dortmund and Bayer Leverkusen, as well as draws against Bayern Munich and Borussia Monchengladbach.
However, they have suffered defeats to Augsburg (twice) and stalemates against relegation-battling Schalke and Mainz.
This has kept the side from going further up the rankings despite punching above their weight against the German giants.
In only their second-ever campaign in the Bundesliga, Urs Fischer's men are looking to finish in the top 10, after finishing below mid-table last year.
Freiburg vs Union Berlin Head-To-Head
In 10 games, the spoils are evenly shared, with Freiburg and Union Berlin both winning four times each.
However, they played out a 1-1 draw in Berlin earlier this campaign.
Freiburg Form Guide (all competitions): D-W-L-W-D
Union Berlin Form Guide (all competitions): L-L-D-L-D
Freiburg vs Union Berlin Team News
Chang-hoon Kwon and Keven Schlotterbeck are both injured. Meanwhile, goalkeeper Mark Flekken is a long-term absentee, having missed the last five months of action with an elbow injury.
Injured: Mark Flekken, Chang-hoon Kwon and Keven Schlotterbeck
The Iron Ones won't have Sheraldo Becker back from his inflammation problem just yet. Meanwhile, Anthony Ujah underwent knee surgery last July, ruling him out for the entire season.
On the bright side, Nico Schlotterbeck returns from his one-game suspension for the red card he received in the loss to Mainz two games ago.
Injured: Anthony Ujah and Sheraldo Becker
Freiburg vs Union Berlin Predicted XI
Freiburg (3-4-1-2): Florian Muller; Philipp Lienhart, Manuel Gulde, Dominique Heintz; Jonathan Schmid, Baptiste Santamaria, Nicolas Hofler, Christian Gunter; Woo-yeong Jeong, Vincenzo Grifo; Ermedin Demirovic.
Union Berlin (3-5-2): Loris Karius; Marvin Friedrich, Robin Knoche, Florian Hubner; Christopher Trimmel, Christian Gentner, Robert Andrich, Marcus Ingvartsen, Niko Giebelmann; Taiwo Awoniyi, Joel Pohjanpalo.
Freiburg vs Union Berlin Prediction
Union Berlin have been impressive this season but form is not on their side at the moment.
We expect Freiburg to secure a point at home and maintain their one-point lead over Union Berlin.
Prediction: Freiburg 1-1 Union Berlin