Argentina striker Lionel Messi’s listless performance in his team’s last two World Cup matches can be attributed to exhaustion, his father said on Thursday.

After a strong start to the 2014 World Cup, Messi, who is widely considered to be the best soccer player in the world, failed to score a goal or record an assist in Argentina’s semifinal victory over Holland. Speaking to Brazilian newspaper Folha de S. Paulo, Messi’s father, Jorge, said that the grueling tournament has taken its toll on the 27-year-old.

“Leo [Messi] said it looked like his legs weighed 100 kilos. He was very tired,” Messi’s father said, according to the Telegraph.

Considered the linchpin of Argentina's offense, Messi played a major role in securing the country’s berth in the 2014 World Cup final. He’s amassed four goals in the tournament, including a game-winning, stoppage time strike against Iran in group play and a pair of scores against Nigeria in the round of 16.

Despite Messi’s diminished performance in Argentina’s last two matches, Germany has developed a plan specifically to stop him during the World Cup final. “We’re not going to reveal it,” Germany’s assistant coach Hansi Flick said.

Argentina and Germany will meet in the 2014 World Cup final on Sunday, July 13, at 3 p.m. EDT. ABC will broadcast the match.