It seems like everything Lars Fischer touches at the minute turns to gold.
Die Eiseren sit second in the Bundesliga, having reduced the gap on leaders Bayern Munich to one point. They have also advanced to the quarter-finals of the DFB Pokal with a midweek win over Wolfsburg.
Mainz, on the other hand, bowed out without so much as a whimper after a 4-0 home defeat to Bayern and sit in 11th in the Bundesliga table.
Union have come out since the winter break with three league wins and that cup victory which, combined with Bayern drawing all three post-break contests 1-1, means they are just a point behind the champions.
Leipzig are one point back with Dortmund and Freiburg another behind them in the tightest title fight in recent memory.
Last week, the men from the red side of Berlin ensured that the bragging rights in the capital city stayed with them as they completed the double over Hertha with a relatively routine 2-0 win at the Olympiastadion.
Goals either side of the break from Danilho Doekhi and Paul Seguin secured the victory. On Tuesday night, Robin Knoche and Kevin Behrens scored to cancel out Luca Waldshmidt's early opener for Wolfsburg. This meant that they were able to weather Niko Giesselmann's late red card and Sheraldo Becker's miss of the season.
Union were the subject of much social media chatter on deadline day as they were on the verge of completing the sensational signing of former Real Madrid and Sevilla forward Isco, a free agent after leaving the Estadio Ramon Sanchez-Pizjuan in December.
A medical was passed before the Spaniard's camp changed their contract demands at the last minute prompting Union to withdraw from the deal. GM Oliver Uhnert was quoted as saying:
"We would have liked to see Isco with us but we have our limits. These limits were exceeded which is why the transfer will not take place."
For Mainz, they won their first game in six last weekend with a convincing 5-2 home victory over relegation-threatened Bochum. This put them in 11th spot, seven points above the drop zone and nine off the European places.
Before that victory, you have to go back to October 21st and a 5-0 win over Koln also at the MEWA Arena for their last victory. During that time they suffered a 6-2 reversal at the Allianz Arena. Tuesday's cup loss was not the first time that Bayern have had their way with Die Nullfunfer.
They got off to a fast start on Saturday against Bochum with Lee Jae-Sung opening the scoring after less than 60 seconds before Silvan Widmer doubled the advantage after a quarter of an hour. Karim Onisiwo was the hero of the day though with a hat-trick which meant that a late flurry from the visitors was nothing more than consolation.
On Tuesday, Mainze were swatted aside by a resurgent Bayern in the Rhineland, which was compounded by Alexander Hack's late dismissal.
Team News
Union will be without the suspended Giesselamann after the red card during the week and Norwegian midfielder Morten Thorsby is still not fit to return. Newest signing, Tunisian international midfielder Aissa Laidouni, made his debut off the bench against Wolfsburg for the last 25 minutes and could well make his first start here.
Kevin Behrens is proving himself to be quite the clutch striker as he came off the bench to score the winner with ten minutes remaining on Tuesday night having also scored the decisive goal in the league win over Werder Bremen on January 25th. He will certainly be pushing for a return to the starting XI.
Urs Fischer has had contributions from all over the pitch all season and has had the luxury of a relatively settled lineup. As the old adage goes - If it ain't broke, don't fix it!
For Bo Svensson's Mainz, they too have a suspension issue with the afore-mentioned Alexander Hack missing after his straight red in the dying embers in the cup game on Tuesday. Other than that, there are no fresh injury concerns for the Danish manager with long-term absentees Suliman Mustapha, Jonathan Burkardt and Robin Zentner not yet fit to return. There is more hope for Delano Burgzorg but this may be too soon for the Dutch midfielder.
French striker Ludovic Ajorque signed from Strasbourg in the January window and has made three appearances without a goal so far and will be hoping to keep his place and prove his worth
Likely Line-ups
Union Berlin: Ronnow; Doekhi; Knoche; Leite; Juranovic; Seguin; Khedira; Haberer; Laidouni; Behrens; Becker
Mainz: Dahmen; Hanche-Olsen; Bell; Fernandes; Widmer; Bareiro-Martins; Kohr; Caci; Lee; Onisiwo; Ajourque
Key Players
The forward has been instrumental in Union's run of great form since the winter break. He came off the bench to score the winner to advance his side into the cup quarter-finals having also scored the winner in the 2-1 win over Werder Bremen a fortnight ago. After a relatively barren start to the season, the experienced forward could be crucial if Die Eiseren are to keep the heat on the league leaders.
Ludovic Ajourque
Since his move from Strasbourg, the French striker has not yet scored a goal or completed 90 minutes in his first three games. With Mainz sitting smack bang in the middle of the Bundesliga table, you have to feel that their season is at a crossroads. A run of results either way could see them making a push for Europe or fighting relegation. Ajourque's goals (or lack of) could be key to establishing which way it goes.
Where is the game being played?
The game is at the home of Union Berlin - Die Stadion an der Alten Foresterei
What time is kick-off?
Kick-off is at 2:30pm GMT
Where can I watch?
The game is not live anywhere in the UK but you can follow all of the view and news right here with VAVEL UK.