Bayern Munich and Borussia Dortmund resume their Bundesliga rivalry this weekend with both sides looking to avoid slipping up in the title race at home against relegation-threatened opposition.
Dortmund, who are six points clear of defending champions Bayern, host second-from-bottom Hanover on Saturday while VfB Stuttgart, who are 16th and also in the bottom-three, are Sunday's guests at Munich's Allianz Arena and are hoping to avoid a fourth straight league defeat.
Bayern coach Niko Kovac has a decision to make about who starts at centre-back for second-placed Bayern with neither 2014 World Cup winners Jerome Boateng nor Mats Hummels, both 30, sure of a starting place.
Kovac has said Niklas Suele is the only centre-back sure of a spot in the 11, leaving the experienced Germany stars to battle for the other berth.
Hummels started last Friday's 3-1 win at Hoffenheim, with Boateng on the bench, because "Mats was just a tiny bit better - we're talking a micron" explained Kovac.
The race is on to see who can convince Kovac they should start Bayern's Champions League last 16 away tie at Anfield on February 19.
Bayern are searching for clues as to why they lag behind Dortmund and midfielder Leon Goretzka has revealed they are attempting to find their weaknesses.
"They (Dortmund) won against us (3-2 last November), they must have worked something about us out," Goretzka, who scored twice in last Friday's 3-1 win at Hoffenheim, told magazine Kicker.
"We have to find out what it was and straighten it out."
Fine-tuning by Kovac
Kovac accordingly put his side through their paces in sub-zero temperatures in Munich this week in a series of small training matches which replicated tight situations.
"In the second half, Hoffenheim created some pressure and that made it harder," explained the Bayern boss.
Stuttgart were thumped 3-0 at home by Bayern when the sides last met in September, but managed a shock 4-1 win at the Allianz Arena in May 2018 after Bayern had already secured last season's title.
Dortmund, who are eager to build on last Saturday's hard-fought 1-0 win at Leipzig thanks to Axel Witsel's strike, are wary of Hanover, a bogey side for Borussia in recent seasons.
Hanover are 17th, with only goal difference keeping them above bottom side Nuremberg, but held Dortmund to a goalless draw when the sides met in August.
After Dortmund crashed to a shock 4-2 defeat at Hanover in October 2017, the leaders are cautious of a similar repeat.
"In the away match, Hanover caused us problems and we will need the same level of concentration as we had at Leipzig," said Dortmund's director of sport Michael Zorc.
Playmaker and captain Marco Reus is set to return after missing the Leipzig win with a twisted ankle.
"Marco has trained the whole week and he's doing well," said coach Lucien Favre about Reus who has scored 11 goals and set up seven more in 17 games this season.
Julian Weigl is one to watch in Dortmund's defence having been converted to a centre-back to avert an injury crisis.
The 23-year-old, whose chances this season have been restricted by the arrivals of Thomas Delaney and Witsel in the defensive midfield, was magnificent against Leipzig, even out of position.
"Julian struggled with injury, then new people arrived in the summer. Despite that, he behaved professionally and was exceptional in his new role," said Zorc.
Fixtures (all times 16:30 SA time unless stated)
Hertha Berlin v Schalke (21:30)
Borussia Dortmund v Hanover, Borussia Moenchengladbach v Augsburg, Freiburg v Hoffenheim, Mainz v Nuremberg, Wolfsburg v Bayer Leverkusen, Werder Bremen v Eintracht Frankfurt (19:30)
Bayern Munich v Stuttgart, Fortuna Duesseldorf v RB Leipzig (19:00)