A very even game which came to life in the second half, but ends all-square. The first goalless draw between these two clubs, but no complaints on either side.
Few chances, fair score
It could well take something like this to win it - Barreiro's shot hits the shoulder of Knoche and curls wickedly wide of the post
Speed check: The fastest player in the game after 90 minutes
Sheraldo Becker 33.62km/h
Maxim Leitsch 31.98km/h
Theoson-Jordan Siebatcheu 31.92km/h
Captain to the rescue?
Mainz club captain Trimmel takes to the field - can he provide the moment of magic Mainz need?
Mainz turning up the heat
No goal against ex-club
Ingvartsen leaves having failed to score agianst his former club, but he won an impressive 15 out of 23 duels - more than any other Mainz player so far this afternoon.
This one arguably more welcome than in the first half, when neither side had really hit top gear.
First touch, on target
Fulgini had an impressive debut last weekend, and he almost made an immediate impact - his first touch of the ball giving Rönnow some work to do.
Not only the way the teams have come out for this second half is encouraging, also the fact this game has never ended goalless in the previous 13 meetings gives us reason to believe there could be a goal just around the corner.
Totally different game
Good chance for Stach
Widmer waltzes into the area and finally gets the ball out from between his feet to tee up Stach, but his low shot goes straight at Rönnow. First chance of the half for Mainz.
Another shot from range
Union are getting on top now and Ryerson rifles in an effort which clears the right-hand post. Two shots in two minutes.
Roof of the net!
This is the closest either team has come to opening the scoring, but Gießelmann's dipping effort lands on the roof of the net.
Subs 'warming' up
Possibly a change on the horizon, Fulgini among the subs warming up their muscles.
The same 22 brave men return to the field for another 45 minutes fighting the heat and seeking to snatch a winner.
No major chances of note with both teams struggling in hot conditions. Mainz chose to play into the sun in the first half, so will they be at an advantage with the sun at their back in the second half? Stick with us to find out!
Very few chances in this first half, with xG quite a clear indication of this.
Chances at a premium
Speed check: The fastest player in the game after 30 minutes
Sheraldo Becker 33.49km/h
Karim Onisiwo 31.86km/h
Silvan Dominic Widmer 31.51km/h
Heat taking its toll
Karim Onisiwo Sheraldo Becker
With the mercury over 30 degrees celsius, it's time for a mid-half cooling break.
Stach on target
The first Mainz shot on target is a daisy-cutter from Stach, which Rönnow is down to collect.
Widmer at the near post
Mainz's first shot of the game comes from their captain Widmer, who meets a corner at the near post, but heads it wide.
Quite a few fouls in the early exchanges and the referee clamps down on it with the first yellow card shown, Onisiwo perhaps paying the price there also for what had happened ahead of his foul.
Change of ends
The teams have swapped sides, so Mainz are shooting from left to right and Union from right to left in this first, sun-soaked half in Mainz.
Sami in the stands
Watching his brother Rani lead Union Berlin out as captain today is Sami Khedira. as the teams emerge.
Age before beauty
Both teams have one thing in common – the average age of each of their starting line-up is 27.8 years. This is relatively young for Union, based on an older average over recent seasons, but it is Mainz's oldest average age for a starting XI since November 2013.
Two changes for Mainz
Two changes for Mainz with Ingvartsen coming in to face his former club, while Widmer is back from illness to replace compatriot Fernandes. Fulgini drops to the bench, despite an impressive debut, to make room for Ingvartsen.
Just one change to the Union team after their derby win, with regular captain Trimmel dropping to the bench and Gießelmann replacing him. Khedira wears the captain's armband this afternoon.
Union starting XI:
Rönnow - Jaeckel, Knoche, Leite - Ryerson, Khedira, Gießelmann – Haraguchi, Haberer – Becker, Siebatcheu
Mainz starting XI:
Zentner - Bell, Hack, Leitsch - Widmer (c), Kohr, Lee, Aaron - Stach, Ingvartsen – Onisiwo
Widmer to return?
Mainz coach Bo Svensson should be able to count on Silvan Widmer for Matchday 2, and the Swiss wing-back and club captain could replace compatriot Edimilson Fernandes in the team. However, Germany U21 skipper Jonathan Burkardt - who struck 11 league goals for Mainz last season - is still unavailable for at least one more week.
Fulgini to strike?
© Getty Images
Union's promising partnership
Having pacy attacker Sheraldo Becker alongside him will help Siebatcheu. The Suriname international - who netted against Mainz last season before signing a new contract over the summer - opened the new Bundesliga campaign with a goal and an assist against Hertha.
Eyes on Jordan
© Getty Images