Nainkin was the personal coach of Wayne Ferreira and currently works with Sam Querrey, as well as many other professional and top junior players. He played collegiate tennis for UCLA, where he played No. 1 singles in 1991. Nainkin played on the ATP World Tour for several years, reaching a career-high ranking of No. 132. In 1998 he advanced to the third round of the US Open and also represented South Africa in Davis Cup Competition in 1998 and 1999.