Reus scored the first and the third while setting up the fourth for Ilkay Gündoðan while Neven Subotic and Jakub Blaszczykowski were on target in a rampant win.
BVB coach Jürgen Klopp rested his top scorer Robert Lewandowski for the first time this season to field summer recruit Julian Schieber with Ilkay Gündogan and Mario Götze the other new faces after the 3-3 draw at Eintracht Frankfurt and the defeat to Hamburger SV in the last two Matchdays, while Mönchengladbach started with Roel Brouwers for the suspended Martin Stranzl and Igor de Camargo came in for Luuk de Jong, who was unavailable due to injury.
The visitors looked good in the first stages when Mike Hanke just failed to get a touch on a deflected pass and Patrick Herrmann's subsequent attempt was cleared at the expense of a corner three minutes into the game. However, Dortmund were soon in the driving seat and upped the pressure, resulting in Gündogan's long-range effort and Reus' good run, although neither got the better of goalkeeper Marc-Andre ter Stegen. The 20-year-old looked beaten after 12 minutes when Neven Subotic connected to a corner, but his header landed on the crossbar.
Despite the Bundesliga champions enjoying the lion's share of possession, Gladbach continued threatening on their frequent counter-attacks. Hanke (21') forced Roman Weidenfeller to punch his 25-yard rocket shot away. When Dortmund's pressure eventually did take its toll after 35 minutes, it was unsurprisingly Reus who supplied the goal as he ran through the guest's defence to coolly stick the ball through ter Stegen's legs.
Subotic eventually got the better of the Germany international when he headed Blaszczykowski's cross into the far right corner five minutes before half-time. Reus should have added a third just before the interval, but didn't get past ter Stegen after a clever pass from Götze.
Like in the first half, Gladbach emerged as the more agile side in the first minutes of the second interval came close to scoring after 51 minutes when Weidenfeller palmed away de Camargo's header. Yet, there wasn't much to be seen from The Foals afterwards in an attacking sense whilst Dortmund, for all their possession, were struggling to be decisive in the final third until the outstanding Reus picked up the ball and beautifully curled his shot over ter Stegen into the far corner twenty minutes from time, effectively deciding the encounter.
Gündogan had no difficulty making it four nine minutes later with only goalkeeper Christofer Heimeroth, who came in for the injured ter Stegen, to beat after Blaszczykowski's assist, and the Poland international struck Dortmund's fifth himself five minutes from time from close range after both de Camargo (83') and substitute Branimir Hrgota (84') had failed to get the ball into the back of the net.
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