Which male tennis player has been ranked no. 1 on the world ranking list most years in a row?

Explanation

American tennis star Pete Sampres (born 1971) stopped his career in the fall 2002 after he had won his 14th Grand Slam title. Seven of his titles were won in the Wimbledon tournament (1993-1995, 1997-2000). In 1990 he became the youngest winner of the US Open at age 19. Sampras ranked as world number 1 for six years in a row in the period 1993-1998, which is a record. Today Sampras is considered one of the best male tennis players ever.