Nydahl started playing tennis at the age of seven. In the junior competition he was in the final of the Swedish Indoor Junior Championships and in the semifinals of the Italian Open Juniors . He became a professional tennis player in 1987 and reached the final of the Challenger tournaments in Bossonnens and Strasbourg the following year . In 1989 he stood in Bologna at the side of his compatriot Jörgen Windahl for the first time in the final of an ATP tournament , where they were clearly defeated by the Spaniards Sergio Casal and Javier Sánchez in two sets. In the following years he focused on the Challenger Tour. In 1990 he won his first double title on the Challenger Tour with Peter Nyborg in Munich , and another double title followed the following year in Bucharest .
In 1993 he won his first individual title on the Challenger Tour in Emden and he was in the double finals at the Swedish Open . In the following years he won several other singles and doubles titles on the Challenger Tour. In 1997 he reached an ATP double final for the last time, but could not win a title on the ATP World Tour. He reached his highest ranking in the ATP world rankings in 1998 with position 72 in singles and in 1989 with position 103 in doubles.
Sweden
Bologna
Sergio Casal Javier Sánchez
Brian Devening
Shanghai
Max Mirny Kevin Ullyett