Bayern Munich restart their charge for an eighth straight Bundesliga title at Union Berlin on Sunday amid doubts the Bavarian giants will be able to last the distance after a two-month hiatus.
Hansi Flick's side hold a one-point lead at the top of the league heading into their trip to the German capital, which has been the scene of some impressive upsets thanks to promoted Union's form at their Alten Foersterei stadium.
Union have twice shocked the league leaders this season, beating Borussia Dortmund 3-1 in August and turning out 2-0 victors over Borussia Moenchengladbach three months later.
Flick is unsure of his team's ability to play out a full match of professional football after having only received the go-ahead to resume full team training last week.
"We don't know if the team can hold out over 90 minutes," said Flick. "We have trained well and played three matches of 20 minutes each last Sunday.
"They were played at a very high intensity, but we don't know clearly where we stand.
The Bundesliga is the first major league in Europe to return to action since the coronavirus brought football to a halt two months ago and has only come back with a host of strict health regulations, chief among them empty stands in what are usually passion-filled stadiums.
That means Union won't be able to count on their ferocious home support at their ground on the eastern outskirts of the German capital.
They will also be without their coach Urs Fischer after breaking the team quarantine following the death of his father-in-law.
"It's not possible to surprise Bayern with the experience their players have," said assistant coach Markus Hoffmann, who will take charge of Union for the Bayern match.
"We have to concentrate on ourselves and try to implement what we can to influence the game in the best possible way."
Bayern's lead was cut to a single point by Borussia Dortmund, who on Saturday showed no ring rustiness in a 4-0 demolition of Ruhr rivals Schalke.
Young gun Erling Braut Haaland was again the headline act, scoring the first Bundesliga goal after the restart and setting up Raphael Guerreiro for the first of his brace.
In one of a series of odd scenes that peppered the first day back, Dortmund's players jogged over to applaud an empty 'Sudtribune', which would for a normal derby would be jammed with 25,000 delirious fans hailing a huge victory that keeps pressure on their title rivals.
"There was no noise. You shoot at the goal, make a top pass, score a goal, and nothing happens," said Dortmund coach Lucien Favre.
"That's very, very strange. We really missed our fans."
As well as the echoing arenas, a host of other rules have been put in place to try to stop the spread of the virus, from frequent testing to masks for players on the subs bench and a week-long quarantine for teams ahead of the restart.
However, advice to socially distance didn't stop Hertha Berlin players from celebrating their goals in a 3-0 win at Hoffenheim by hugging each other.
"The fact is that this is part of football," said Hertha coach Bruno Labbadia. "We've been tested so many times that we can allow it.
"If you can't celebrate anymore, the whole thing breaks down."
A German Football League (DFL) spokesman confirmed there will be no punishment, as it had only offered "guidelines" on how goals should be celebrated.
The DFL has also made no secret of the fact that several clubs are in a dire financial situation as a result of the lockdown.
If they are able to complete the nine remaining rounds of matches by June 30, clubs could receive around 300 million euros ($324 million) from television contracts.
Clubs in England, Spain and Italy, where leagues are weeks away from returning, will be watching to see how the rest of weekend goes.
