Germany captain Manuel Neuer said on Tuesday top players are at their physical "limits" due to this season's condensed fixture list resulting from the knock-on effects of the coronavirus pandemic.
Neuer has already made 14 appearances for club and country in seven weeks since the campaign started.
"There has never been a season like this before and hopefully there will never be again," the Bayern Munich goalkeeper told website Sportbuzzer.
Neuer gets a rare break on Wednesday with Eintracht Frankfurt's Kevin Trapp in goal for Germany's friendly against the Czech Republic in Leipzig.
However, the 34-year-old Neuer is expected to return for Saturday's Nations League match against Ukraine, and away to Spain on Tuesday.
With less than a month separating last season's Champions League final, won by Bayern, and the 2020/21 term, Neuer said top players have little time to rest with matches every three to four days.
"Certain training exercises are no longer possible - there is recovery after the game, a bit of tactics, the final training session, and then the next game is already on the agenda," he said.
However, he admits professional footballers should be grateful to be playing at all after Germany posted a record high 23,399 new cases of the coronavirus last Saturday.
"We as players should not complain, even if we have reached our limits - we're allowed to play, in contrast to many others (sports)," he said.
"We are very happy about it, you only have to look at the amateur footballers or dare to take a look at other sports," he added.
Germany coach Joachim Loew backed up Neuer and criticised the dense fixture list.
For the first time in Loew's 14 years in charge, the Bundesliga winter break has been slashed from four weeks to just two over Christmas, with matches resuming on January 2.
"The fixture list is too full -- too much is being put on the players," Loew said in Leipzig.
"If we coaches don't exercise the utmost caution now, we'll have a big problem next year," he warned.
In a thinly-veiled dig at UEFA, Loew warned if Europe's top nations want fit players "next March or April" to prepare for the European Championship, "those responsible for the schedule must put their heads together".