Marco Reus shone as Borussia Dortmund opened a nine-point lead over Bayern Munich at the top of the Bundesliga table with a 5-1 rout of strugglers Hanover on Saturday.
With defending champions Bayern hosting Stuttgart on Sunday, Dortmund grabbed the chance to thump second-from-bottom Hanover with Reus causing havoc on his return from an ankle injury.
Lucien Favre's side floored Hanover with three goals in seven minutes.
Achraf Hakimi, who is on loan from Real Madrid, Reus, Mario Gotze and Raphael Guerreiro scored Dortmund's goals to keep them on course for their first Bundesliga title since 2012.
The rout piles pressure on Hanover coach Andre Breitenreiter, but his side showed spirit when Marvin Bakalorz scored a late consolation against his former club before Witsel grabbed Dortmund's fifth goal on 90 minutes.
Borussia Moenchengladbach joined Bayern on 39 points, but went second on goal difference with a 2-0 win at home to Augsburg.
Gladbach midfielder Jonas Hofmann, linked with a move to Tottenham Hotspur, had a penalty saved just before the break before Oscar Wendt and Patrick Herrmann scored second-half goals.
Bayer Leverkusen claimed their first win under new coach Peter Bosz when Germany internationals Kai Havertz, Kevin Volland and Julian Brandt scored their goals in a 3-0 victory at Wolfsburg.
Hoffenheim moved into the top six with a 4-2 win at Freiburg as Andrej Kramaric scored twice while mid-table Mainz won 2-1 at home to bottom side Nuremberg with Sweden striker Robin Quaison scoring the winner.
On Saturday night, Eintracht Frankfurt climbed into the top four with a 2-2 draw at Werder Bremen as striker Sebastian Haller equalised with a second-half penalty for the visitors.
RB Leipzig can regain fourth place by avoiding defeat at Fortuna Duesseldorf on Sunday evening.