Pless started playing tennis at the age of seven. He has been active on the junior tour since 1996 and won the Australian Open against Michail Juschny in 1999 . He also reached the finals of Wimbledon (loss to Jürgen Melzer ) and the US Open (loss to Jarkko Nieminen ). At the end of the year, Pless was number 1 in the junior world rankings.
From 1999: professional career
Pless was initially active on the Challenger Tour and won eight titles in his career, four each in singles and four in doubles. At the ATP level , he made it into a semi-finals three times, and in Grand Slam tournaments he never got past the second round. Nevertheless, due to constant results, he was able to achieve his best position in the world rankings on January 28, 2002 with rank 65. After a serious shoulder injury, he fell far down the rankings in 2003. It was not until 2006 that he made another jump into the top 100, where he was able to stay until September 2007. At the end of 2010 he finally fell out of the world rankings.
He took part in the 2000 Olympic Games in Sydney , where he took part in the individual competition. In the first round he defeated the Armenian Sargis Sargsian 6: 3, 6: 4, but had to admit defeat to the Australian Mark Philippoussis 4: 6, 4: 6 in the following round .
Pless played eight games for the Danish Davis Cup team between 1999 and 2012 , seven of them between 1999 and 2001. In the 2012 season , after an eleven-year Davis Cup abstinence, he surprisingly played against Slovenia . Pless played his last professional match to date on September 28, 2009.