Ailien Poese made two changes at the break, bringing Naika Reissner and Lisa Heiseler on for Heikkinen and Moraitou, like-for-like. And immediately Reissner caused panic as she drove into the Mainz box from the left, in a scene familiar to all who have watched Union so far this season.

Heiseler, too, seemed to add a little pace and bite into the middle, taking a short pass from Steuerwald superbly, then forcing Heidrun Sigurdardottir to make an excellent, well-timed challenge, as she turned in the box, moving the ball onto her trusty left foot, ready to shoot.

But Mainz too were looking to advance more readily as the second half wore on, especially through the dangerous Bouziane, who drew a fine tackle first from Aehling, then crossed cleverly across the box where Steuerwald hoicked the ball clear. This was the cue for Poese to make her next attacking change, bringing on Sophie Weidauer on for Janež.

Still Union controlled the ball, but still they came up against a brick wall every time they got into the final third. Dina Orschmann tried to thread a pass through towards Campbell, Weidauer lobbed a cross deep towards the head of Heiseler. At the toher end, Bouziane evaded the challenges of Steuerwald, but scuffed her shot straight at Bösl. That was by the by, however, as while she turned, Aehling had gone down heavily, to be led off, a grimace on her face, clearly hurt.

Tomke Schneider took her place on the left with just over fifteen minutes to play. She got a yellow card almost immediately for a lunge on Bathmann.

Then, with just over 15 minutes to play, Union made the breakthrough after a fine, sweeping move. Pawollek advanced up the middle, finding Reissner, who laid the ball off for Heiseler. Union’s captain then found Eileen Campbell with a pinpoint cross for Campbell to claim her first competitive goal for Union, leaping in the box and planting a fine header past Matsumoto.

Union, now becalmed, were now posing more of a constant threat. Reissner slipped Weidauer through, but Matsumoto cleared up. Schneider won a corner that the keeper then punched clear under pressure.

But Mainz weren’t to be brushed aside as easily as that, and Union of course could cast their minds back to the same round last season, when they needed a penalty shoot-out to advance past Gütersloh. Vital Kats suddenly found herself free, but Weiß managed to get to her just in time to force her back, and the chance evaporated away, as quickly as it had appeared.

With two minutes to go, Campbell got her second, running onto the longest of clearances, and taking the ball from almost inside her own half before slotting it under the sprawling Matsumoto. It was a cool, striker’s finish.

It was a battle, and thoughts turned immediately to the injured Aehling. But, crucially, Union were guaranteed a place in the next round.