Career
Sakai, a student of Waseda University, competed in the 1970 Summer Universiade, which was held in Turin, Italy. Sakai made the third round of the 1971 United States Open, beating Vitas Gerulaitis and Ross Case. At Wimbledon in 1973, Sakai was eliminated in the third round by Ilie Năstase, having earlier secured wins over Frew McMillan and Hans Kary.
In Osaka later that year, he beat Zeljko Franulovic in the semi-finals to make it into his first Grand Prix final, which he lost to Ken Rosewall.
He had his best Grand Slam performance at the 1974 French Open, where he reached the third round of the singles draw and was a quarter-finalist in the men"s doubles, with Kenichi Hirai. The same player partnered Sakai in the Düsseldorf Grand Prix tournament that year and the pair finished as runners-up.
He took part in a total of 19 ties during his career.