Bayern have won all four of their opening German league matches this season, but had to come from behind to force a 2-1 win at home to Bavarian rivals Augsburg on Saturday with two late goals.
Now the 2013 Champions League winners switch their focus to Europe at Olympiakos when they kick off their Group F campaign, but Guardiola is warning they can ill afford another below-par display with Arsenal also in their pool.
“Everyone has to give their all there and put in 100 percent on the pitch, or things can go astray,” warned Bayern’s head coach.
“Our body language in the first half wasn’t good (against Augsburg) and our play was much, much too slow.
“I hope we can improve in the future. We have to play for 90 minutes, not just 45.”
Bayern are second in the Bundesliga table on goal difference behind Borussia Dortmund, while Marco Silva’s Olympiakos top the Greek Superleague table as the only team with three wins from three matches.
Mario Goetze is expected to return after Bayern’s 23-year-old Germany international forward missed the Augsburg win with a leg injury, but was back in training on Sunday.
Guardiola will be without wingers Franck Ribery and Arjen Robben.
Ribery has missed the last six months with an ankle injury while Robben is out for a month with a groin problem.
Starting with Olympiakos, Bayern play three games in six days as they face newly-promoted Darmstadt on Saturday in the Bundesliga, then host last season’s Bundesliga runners-up Wolfsburg on Tuesday September 22.
The Bavarian giants had to dig deep against Augsburg after Alexander Esswein put the visitors ahead on 43 minutes before Robert Lewandowski equalised on 77 minutes, then Thomas Mueller kept his cool by converting a 90th-minute penalty.
Munich finished with 80 percent of the possession, dominated the shot count 27-4 and had nine corners to the visitors’ none, but the home camp was far from happy with the first 45 minutes.
“We were asleep for the first half and lacked pace,” said captain Philipp Lahm.
“We have to learn from this. It’s not good enough, and that includes in the Bundesliga.”
And Lewandowski admitted the Bavarians can expect a tough Champions League opener away from home.
“We’re looking forward to Wednesday’s match, and we’re obviously hoping to start a winning run in the Champions League too,” said Lewandowski.
“It won’t be easy, especially away from home. We have to play well from the start. We have to go for it.” – Agence France-Presse