Bayern thrashed Rostov 5-0 in their Champions League Group D opener but midfielder Xabi Alonso warned they will come under much greater scrutiny against Atletico, who have conceded two goals in seven games in all competitions.
"We're happy with the start we have made but we know that this is the first really powerful team we're going to face. What we've achieved up to now could all fall apart in 90 minutes," Alonso told Spanish newspaper Marca on Monday.
Atletico knocked Bayern out of the competition last season on away goals in a thrilling two-legged tie and Alonso is expecting more of the same from Diego Simeone's side.
"I think they are a very similar team to last year, they are competitive, hard working, always well organised. They have positive aggression, they always compete to the limit."
Ancelotti has won a joint-record three Champions League titles, his 2014 triumph coming at the expense of Atletico with local rivals Real Madrid. The Italian also oversaw Atletico's elimination at the quarter-final stage the following season.
For Alonso, the Italian coach, who also had two Champions League triumphs with AC Milan, has not altered much since succeeding Pep Guardiola in the summer.
"The base has been here since the team won the triple (Bundesliga, German Cup and Champions League in 2013)," Alonso said, "There's a very important nucleus in the team and everyone who comes to the team works alongside that core.
"When you have a built-in idea and a winning project everything is much easier. We haven't changed too much."
Atletico overcame 10-man Deportivo La Coruna 1-0 on Sunday but their fourth straight win in all competitions was soured by a serious knee injury to midfield anchor Augusto Fernandez, who has been ruled out for seven months.
Atletico defender Jose Gimenez is also unavailable with a calf problem while Bayern will be without Holger Badstuber and Douglas Costa through injury.
(Editing by Rex Gowar)
