Marco Reus scored his first goal since returning from a nearly nine-month injury layoff as Borussia Dortmund secured a 1-0 victory at Borussia Monchengladbach.
Reus, in his third appearance since injuring a knee in the DFB Pokal final against Eintracht Frankfurt in May, slotted home the winner in the 32nd minute.
The victory moved Dortmund second in the Bundesliga on 40 points -- 19 behind runaway leaders Bayern Munich -- with third-place RB Leipzig still yet to face Frankfurt on Monday.
It was also the sixth consecutive victory for Dortmund over Gladbach in the Borussen derby and left them unbeaten in their last eight Bundesliga games, dating to Dec. 9.
Andre Schurrle's cross from the left side of the box was left alone by Mario Gotze and made its way to Reus, who fired with his right foot and drilled the crossbar.
Gladbach, who have now lost their last four league games and failed to score in any of them, thought they had the equaliser in the 42nd minute.
Lars Stindl's shot was deflected and ended up at the feet of Jannik Vestergaard, who easily beat goalkeeper Roman Burki, but the video assistant referee (VAR) ruled that Vestergaard was offside.
Thorgan Hazard nearly followed with his own chance just before halftime, but he sliced it off his right foot from the right of the box and sent it wide.
Reus almost bagged a second goal in the 61st minute when Gotze's corner landed in the box between Dortmund's Michy Batshuayi and Gladbach's Reese Oxford, but his volley was caught easily by keeper Yann Sommer.
And Gladbach had one last chance in added time but Vestergaard was held by Sokratis and despite pleas was not awarded a penalty.
Dortmund have only lost away from home twice this season, yet the game was the first since the 2015-16 season that they did not score at least three goals against Gladbach.
Players on both teams struggled all game with an uneven pitch that appeared patchy and inconsistent in several areas.