Sakai was born in Niigata Prefecture on March 14, 1991.He joined J1 League club Albirex Niigata from their youth team in 2008. he played many matches from 2009. In January 2012, he moved to German Bundesliga club Stuttgart. He played 87 matches for the club in 4 seasons. In summer 2015, he moved to Hamburger SV. Although he played many matches for the club, the club was relegated to 2. Bundesliga first time in the club history end of the 2017/18 season. In summer 2019, he returned to Japan and joined Vissel Kobe. Kobe won the champions in the 2019 Emperor's Cup which is first major title in the club history.