Nakamura was slated by the Japanese media for what was a poor display against Colombia - and he took it to heart. He said: "I took a week off before starting self-training. I want to join the squad in fine shape and be 100 per cent fit."

Naka is not worried that so many games will sap his energy for the start of the new season.

"Gordon Strachan knows the situation," said the Japanese who played in 50 of Celtic's 52 games this season.

"Before this season I had the World Cup and there were times when I would have two or three days off when everyone else was training. I will be ready for the Champions League qualifiers in August, no problem."