The Venezuelan whipped in a stunning first-time effort within five minutes of substitute Mike Hanke opening the scoring in a game in which, until the goal, Gladbach had very much been second best.
As expected, Foals coach Lucien Favre rang the changes after fielding a largely second-string eleven in the UEFA Europa League on Thursday night, and it was the fresh legs of Patrick Herrmann that were doing plenty of early running. Twice the midfielder attempted to get in behind Bo Svensson, with the Mainz defender doing just enough to see off the danger.
It was the visitors, though, who strung together the first chance of note as Adam Szalai cushioned Eugen Polanski's long pass into the path of Andreas Ivanschitz. The Austrian got plenty behind it, but Gladbach keeper Marc-Andre ter Stegen was able to get down early and push the ball to safety.
Hanke strikes first
When Gladbach did get forward, it was no surprise to see Arango involved. That said, the Venezuelan was unable to make anything of what by his standards was a very presentable free kick in the 35th minute. The hosts only threatened in fits and starts for the remainder of the half, with Mainz instead showing the greater initiative and going close to taking a first-half lead through Shawn Parker.
Favre reacted to his side's limited first-half showing with the introduction of target man Hanke, and it was a change that paid off as Gladbach took a 58th-minute lead. The substitute started the move, while Harvard Nordveidt had the wherewithal to spread the play out wide for Tony Jantschke to drive the ball back across goal and onto the boot of Hanke for 1-0.
Arc it like Arango
Mainz threatened an immediate response through Polanski, before Arango doubled his side's advantage with one of the goals of the season. Mainz goalkeeper Heinz Müller was forced out of his area to clear from Herrmann, but could only watch on as Arango guided the loose ball, first time, over the hapless goalkeeper and into the back of the net from a good 45 yards.
Mainz became increasingly exposed as they searched for a way back into the contest, and had captain Nikolce Noveski to thank for not falling further behind, with the defender timing his challenge to sheer perfection as Herrmann raced into the box with 10 minutes left on the clock. Thomas Tuchel's charges plugged away until the last, but Gladbach held firm to record their sixth Bundesliga win of the season.
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