Germany skipper Michael Ballack said that he is confident he will be in the team's starting line-up for their World Cup opener against Costa Rica on Friday. The 29-year-old midfielder, who picked up a calf injury during the team's training on Monday, insisted that he is recovering well and that he should be fully fit for the Costa Rica game. "I've spent the morning in the weights room and will take part in the team's training session in the afternoon," Ballack was quoted as saying by Sky Sports on Tuesday. "I assume that I'll be able to play on Friday," Ballack added. The Chelsea new-signing added that the German medical staff said that he only needs a one-day rest before returning to the team's training. "Michael is making progress, but he's not fully fit yet, we hope that he can take part in Wednesday's training with the team," team doctor Hans William Mueller was quoted as saying by the German Football Federation (DFB) on their official website. Germany will meet Costa Rica in the World Cup opening game staged in the Allianz Arena on Friday before facing other Group A contenders Poland and Ecuador.