The Bundesliga resumes this weekend after the winter break with one key question looming: can new boys RB Leipzig sustain their challenge to Bayern Munich's domination?

Bayern claimed a record fourth straight Bundesliga title last season, in Pep Guardiola's final year, and under his successor Carlo Ancelotti they have reassumed their place at the top of the German league table.

That is apart from three weeks, ending in mid-December, when RB Leipzig temporarily knocked them off their perch.

Order was restored with Bayern returning top, albeit on goal difference, before RB Leizpig were then dealt a 3-0 hammering in Munich on December 21 with all goals coming in the first half.

Bayern are at Freiburg on Friday in the first round of league games in 2017 and three points ahead of Leipzig, who have a tough restart.

On Saturday, RB host fourth-placed Eintracht Frankfurt, then Hoffenheim -- the only team still unbeaten in Germany's top flight -- before playing Borussia Dortmund away.

RB Leipzig's recent results in friendlies ahead of the second half of the season have been erratic.

They were thrashed 5-1 by Ajax at their Portugal training camp, but then beat Rangers 4-0 in Leipzig last Sunday.

"We have improved from game to game, we are fresher and had a good dress rehearsal against Rangers," said coach Ralph Hasenhuettl.

"With the exception of Ajax, we have prepared well and I am convinced we will be in top condition against Frankfurt."

Sweden midfielder Emil Forsberg, suspended for their next three games, will be missing and playmaker Naby Keita is struggling to be fit for Frankfurt with a back injury.

But Timo Werner, Leipzig's top scorer so far with nine goals, says their pre-Christmas hammering at Bayern has hardened the squad's resolve.

"Even on a good day, it would have been very hard to take some points, because Bayern were very good," the 20-year-old told Bild.

"Nevertheless, it has also made us more hungry, because it's shown us our limits, what is still missing, in order to really have some bite at the top."

Leipzig's goal, says Werner, is to work hard and keep learning to still be in the title race when they host Bayern on May 13 -- the penultimate weekend of the Bundesliga season.

RB are currently on course for a Champions League place next season and, unlike Bayern, can focus solely on the Bundesliga, following their German Cup first-round exit last August.

Leipzig have already punched above their weight this season.

The club, backed by energy drinks giants Red Bull, was founded in 2009 and reached the Bundesliga with four promotions in seven seasons.

They then set a league record by going unbeaten in 13 games at the start of their first season, fuelling belief they can end Bayern's reign.

"If a team can manage to do it this season, then it's Leipzig. Perhaps," Hertha coach Pal Dardai said cautiously.

There are justified concerns RB Leipzig's young squad, whose average age is 24, does not have the experience to sustain their early pace.

"The second half of the season will be harder, because the clubs now know what to expect against Leipzig and they will adjust appropriately," forecasted Frankfurt's sports director Fredi Bobic.

A warning to Leipzig comes in the shape of Wolfsburg, who were second to Bayern in 2014/15 and reached last season's Champions League's quarter-finals but are currently battling relegation.

Hans-Joachim Watzke, CEO of sixth-placed Dortmund, who are nine points behind Leipzig, is respectful of what RB have achieved, but says their final placing in May is what counts.

"The only clubs who have been around the past few years are Bayern and us," Watzke told Die Welt.

"A year and a half ago, it was also predicted that Wolfsburg will constantly surpass us (Dortmund).

"I said at the time 'a swallow doesn't make a summer' and in Leipzig all the usual mechanisms are now in motion.

"Many of their players are now being contacted by other clubs and they will have to deal with setbacks."