Bayern Munich midfielder Xabi Alonso believes that Atletico Madrid have a great chance to win the Champions League after coming up short against the Spanish club in the competition for the second time this year.
The Bundesliga giants lost 1-0 at the Vicente Calderon on Wednesday to see their perfect run under coach Carlo Ancelotti end.
Atletico had already inflicted a 1-0 home defeat to Bayern in Spain earlier in 2016 en route to reaching last season's Champions League final, which they lost on penalties to Real Madrid.
Alonso, a former Spain international, told Onda Cero: "Atletico's game hasn't surprised us as last season it was a similar game. But it was a level affair.
"Without a doubt, I see them as serious candidates for the title. They have the experience, they came close [last season] and they are a great side.
"Atletico are a complicated team to face. It's always difficult to play at the Vicente Calderon stadium."
Atletico, coached by Diego Simeone, also lost in the final of the Champions League in 2014 in Lisbon to Real when Alonso was a Los Blancos player, although he missed the game through suspension.
Bayern dominated possession on Wednesday but Atletico were faster to the ball when the German club attacked and ran almost 8.5km more than their opponents.
"They were effective and we weren't," Alonso said. "When Atletico go 1-0 up, they know how to work to defend their lead and use time to their advantage."
Alonso, whose side had won all of their previous eight games under new coach Ancelotti, is confident his side will bounce back.
"This is only the group stage and it's a minor setback," he said. "There are still four games to play in the group and we hope to turn things around."