Gladbach went close to taking the lead on 16 minutes when Jens Castrop’s bouncing sidefooted effort beat Mainz goalkeeper Daniel Batz - who was making his first appearance since December 2023 - only for covering defender Maxim Leitsch to clear off the line.
Mainz’s respite looked to only be brief, though, as from the resulting corner, Luca Netz’s delivery was nodded on by Kevin Diks, with Leitsch heading into his own net.
However, the goal was ruled out following a VAR check for a handball by Yannik Engelhardt, a decision that, although adhering to the letter of the law, looked extremely harsh given that the contact with the midfielder’s arm was minimal at best and was not what caused the ball to cross the line.
At the other end, it was plain to see why Mainz have struggled in attack so far this term, failing to muster a single shot, on or off target, before half-time.
Mainz interim boss Benjamin Hoffmann opted not to make any substitutions at the break, though, and less than three minutes after the restart, the hosts had a massive chance to open the scoring, with Nelson Weiper - one of seven changes following their 4-0 loss to Freiburg last weekend - firing tamely at Moritz Nicolas after being found by Kaishu Sano.
Castrop then had his second big chance of the evening as he was denied superbly by Batz after the ball had fallen kindly to him.
From Rocco Reitz’s ensuing corner, however, Gladbach forward Haris Tabakovic’s header hit the unfortunate Danny da Costa and went in.
Weiper was then left frustrated again after heading Lee Jae-sung’s cross horribly wide from close range while unmarked, before Gladbach reminded Mainz of their threat when Batz got down low to thwart Shuto Machino, with the visitors ultimately securing a hard-fought victory.
It was the 24th consecutive Bundesliga game without a clean sheet for Mainz, and as they bid to end their nine-match winless run in the league (D2, L7), things are set to get much tougher against reigning champions and rampant leaders Bayern Munich next Sunday, while Gladbach’s win has taken them into the top half as they next face struggling Wolfsburg next Saturday.
Flashscore Man of the Match: Nico Elvedi (Gladbach)