Thomas Muller insists Bayern Munich must give "100 per cent in every match" if they are to defend their Bundesliga title successfully.
Pep Guardiola's side were given a stern test by Schalke on Saturday, with Muller's injury-time goal ultimately sealing a hard-fought 3-1 victory.
The Germany star accepts teams are becoming increasingly defensive when taking on the leaders and he has warned that any let-up in their efforts could prove costly.
"You have to work hard for every single victory in the Bundesliga," he said after the match. "Our opponents make it difficult for us, the back five is quite popular at the moment.
"Our opponents try everything, so we have to give 100 per cent in every match. We played reasonably well. It was annoying to concede the equaliser from a counter-attack."
Bayern now turn their attentions to the Champions League, with Greek title-holders Olympiacos visiting the Allianz Arena on Tuesday.