HAMBURG, June 14 - Costa Rica will try to exploit frailties in Ecuador's defence when the teams meet in World Cup Group A on Thursday, said coach Alexandre Guimaraes.

"Ecuador are a good team but they have weaknesses, especially in defence, which we can exploit," Guimaraes told reporters after training at the AOL Arena on Wednesday.

Costa Rica must win in Hamburg after losing their opening fixture 4-2 to hosts Germany. Ecuador began their challenge with a 2-0 victory over Poland.

"We are going in to the game in an attacking frame of mind and it is simple, we must win," said the 46-year-old coach, who acknowledged his side had a few problems at the back.

"We will have a very different defensive structure from the German game, which we have practised well," he said. "We are confident it can work."

Costa Rica are playing in their third finals.