Nadeshiko Japan was stunned 2-1 by Denmark in their Group C opener of the Algarve Cup on Wednesday.

Sanne Troelsgaard scored early and set up Denmark's second by Johanna Rasmussen. Kozue Ando leveled midway through the first half for Norio Sasaki's side, which is trying to lift Japan's first Algarve Cup.

"It was a tough battle and we couldn't get into a rhythm of any kind," Sasaki said. "We fell asleep at the start of the game. Everyone needs to remind themselves how difficult the first match of any competition can be."

World champion Japan fell behind fast, going down a goal in the second minute when Troelsgaard struck from congestion in the penalty area.

Ando equalized off the post 15 minutes later, sweeping home the rebound of Yuki Ogimi's effort as the two teams went into the break on even terms.

However, Troelsgaard spelled trouble for Japan again two minutes to the hour, breaking free down the right to cross for Rasmussen, who hit past goalkeeper Erina Yamane on her first touch for the decisive goal.

"We went into the game determined to win and we couldn't," veteran midfielder Ando said. "Our work is cut out for us."

Captain and former Asian player of the year Aya Miyama was slightly harsher than Ando on her team.

"It means nothing if we lose," Miyama said. "I feel absolutely terrible. We've got to be more accurate when we attack. We're not allowed to lose. We need to sharpen up once again."

Japan's next game is on Friday against host Portugal.