Koskei was one of the best Kenyan 800m competitors in the 1980s, setting fast times, but lacked success at the international major championships. His breakthrough year was 1982 when the youngster broke 1:45 second barrier for the first time in his career. That same year he made 800m final at the Commonwealth Games in Brisbane, but finished a distant last. Same fate befell Sammy at the World Championships in Helsinki in 1983, this time in the preliminaries.
