The weekend's late kickoff will prove to be a fascinating contest in demonstrating which David may go on to challenge the Goliath of Bayern Munich for the Bundesliga in May.
Match preview
After both qualifying for the Europa League group stages last season, Freiburg and Union have established themselves as two of the league's foremost competitors.
Faced with an undying leviathan in Bayern, the clubs' canny direction, efficient recruitment and long-term coaching strategies have allowed the two teams to make steady progress in recent years, rivalling the waning forces of more reputable teams such as Hoffenheim, Borussia Moenchengladbach and Wolfsburg.
Indeed, both Freiburg's Christian Streich and Union's Urs Fischer have been at their clubs for a combined 15 years, a rarity in modern club football. In that time, Streich and Fischer have moved from 2.Bundesliga hoverers to fully-established top-tier contenders.
Apart from coming unstuck against more heavyweight German opposition - most recently a 3-1 defeat in midweek against RB Leipzig - Freiburg boast an impressive record in the league. This season, they have maintained a fine away record of four wins in eight matches, and a good home record to boot with four wins in six.
Streich's men finished as undisputed winners of Group G of the Europa League too, winning all of their opening four fixtures and remaining undefeated in the group stage.
The boys from Breisgau owe much to their dynamic Austrian forward Michael Gregoritsch, the former Augsburg lynchpin bagging nine goals and two assists in all competitions.
After breaking Koln's counterpress early in the second half last weekend, Gregoritsch strode into the opponent's half to set up Jeong Woo-yeong's first league goal of the season, before capping off a killer display with his team's second, heading in Christian Gunter's cross at the near post.
Italian forward Vincenzo Grifo has equally been one of the Bundesliga's best players this season, with eight goals and three assists from midfield for Die Schwarzwaelder.
However, Streich will have been left disappointed by their inability to compete with Leipzig in midweek. Despite snatching a goal courtesy of Lukas Kubler's belter, their concession of two goals after the restart and later a silly penalty will have been underwhelming for a side on the ascendency this season.
Freiburg will be coming up against an Union Berlin side with much to brag about themselves this season, of course.
Union's stalwart defence, led by the impressive Danilho Doekhi, as well as the sturdy form of Dutch forward Sheraldo Becker, has led to their continued settlement near the top of the Bundesliga table.
However, Union's recent form will have brought a swift reality check for head coach Fischer. Last month saw them lose away to relegation candidates Bochum, not to mention their 5-0 drubbing at the hands of Bayer Leverkusen last weekend.
In midweek, Die Eisernen were unable to hold their mettle against an Augsburg team sitting in the bottom half of the league. Despite having much of the ball and the lion's share of the chances, the incision of Augsburg's counterattack saw Florian Niederlechner take advantage of some lackadaisical defending with a brace.
Indeed, though the 2-2 result against Augsburg may have been forgiven in previous seasons, it should not be given a pass so easily for a side vying for a Champions League place at the end of this campaign.
Union will have to overcome the considerable lethargy of their recent performances against a Freiburg side on just as much if not greater strain of optimism this season.
The Black Foresters' home record is as solid as the spruces lining the region, and it will be one of the toughest challenges of the season for Fischer's Eisernen.
Freiburg Bundesliga form:
D
L
W
W
W
L
Freiburg form (all competitions):
W
D
W
D
W
L
Union Berlin Bundesliga form:
W
W
L
W
L
D
Union Berlin form (all competitions):
L
W
W
W
L
D
Team News
Freiburg will likely welcome the Italian Grifo back into the starting line-up this weekend, the forward having started on the bench against Leipzig in midweek. Ghanaian forward Daniel-Kofi Kyereh may return to the bench after being sidelined with a fever in the last week.
Centre-back Manuel Gulde has missed Freiburg's recent set of matches, having been unable to return to full fitness in training this month. It is unlikely that his manager will call upon him for the team's last fixture before the World Cup break.
Christian Streich will remain without Jonathan Schmid at right-back and Kimberly Ezekwem at left-back, the latter having missed all of this season due to an ongoing tendon problem.
Captain Rani Khedira will definitely miss the tie against Freiburg having picked up his fifth yellow card of the season. Instead, Morten Thorsby will most likely come in to replace Khedira on Sunday.
Meanwhile, Jordan Siebatcheu may return to Union's attack, with Fischer having gone with Kevin Behrens to partner Becker up front in midweek.
Siebatcheu missed out on the USA World Cup squad, and the American will no doubt be looking to enter the winter break with some optimism to counter this disappointment.
Star goalkeeper Frederik Ronnow remains out of contention for this tie, with his hopes of a World Cup spot remaining in the balance for the Dane. The young loanee Lennart Grill will have to up his game after two disappointing runouts as Ronnow's replacement.
Freiburg possible starting lineup:
Flekken; Kubler, Ginter, Lienhard, Gunter; Eggestein, Hofler; Doan, Jeong, Grifo; Gregoritsch
Union Berlin possible starting lineup:
Grill; Baumgartl, Knoche, Leite; Trimmel, Thorsby, Seguin, Haberer, Ryerson; Siebatcheu, Becker
We say: Freiburg 2-1 Union Berlin
Though it is expected to be a fiercely-contested match between the two top-four candidates, Freiburg's excellent home record and more consistent recent form gives Die Breisgau-Brasilianer the slight edge against their Berliner counterparts.