Outsiders Senegal have made a scorching start to their World Cup to reach the quarter-finals at their first attempt, but their coach is concerned they may not be warming up properly before each game.
The African side, conquerors of holders France in their opening game, started slowly in their second-round clash with Sweden on Sunday, conceding an early goal before hitting back to win 2-1 in extra time thanks to two goals by Henri Camara.
The game in the western Japanese city of Oita was played in sweltering temperatures but Metsu says his team made a slow start because they were not warmed up properly.
"We warm up for 45 minutes before the kick-off, then go back into the dressing room for 20 minutes," he told Senegalese reporters.
"We have to because that's the organisers' protocol. Basically, it's as if we haven't warmed up."
Metsu is now considering continuing the warm-up in the dressing-room as a possible solution.
As Africa's last remaining representatives, Senegal have taken the World Cup by storm under their inspirational French coach, who also led them to the final of the African Nations Cup earlier this year.
They face either co-hosts Japan or Turkey in the last eight on Saturday. Cameroon are the only African team to have previously reached the World Cup quarter-finals, losing 3-2 to England in 1990, but Metsu says Senegal's best is yet to come.
"Sweden was not the best we can play," he said. "We struggled with the intensity and the pressure. It was a spectacular match, but not our best. There are always things to work on."
Senegal were due to arrive in Osaka and hold a training session on Tuesday as they begin their preparations for Saturday's encounter.
Metsu is hoping the defensive quartet of captain Aliou Cisse, Pape Malick Diop, Ferdinand Coly and Omar Daf can all shrug off minor injuries for what will be the biggest game in Senegal's -- and maybe in Africa's -- football history.