Sakai was born in Nagano Prefecture on April 12, 1990. He joined J1 League club Kashiwa Reysol from their youth team in 2009. He did not play in the match and Kashiwa was relegated to J2 League end of the 2009 season. He debuted in 2010 and Kashiwa won the champions in 2010 J2 League. In 2011, he became a regular player as right side back and won the champions in J1 League. In July 2012, he moved to German Bundesliga club Hannover. He played 92 matches for the club in 4 seasons. However Hannover was relegated to 2. Bundesliga end of the 2015/16 season. In 2016, he moved to French Ligue 1 club Olympique Marseille.