Juniors Pless had an excellent junior career, winning the
1999 Australian Open Boys' Singles (defeated
Mikhail Youzhny), and reaching the Boys' final at both
Wimbledon (lost to
Jürgen Melzer), and the
US Open (lost to
Jarkko Nieminen) the same year. He finished 1999 as the No. 1 ranked junior player in the world.
Pro tour He turned professional in 1999, and on 28 January 2002, Kristian Pless reached his career-high
ATP singles ranking of World No. 65. He has won tournaments at the
Futures and
Challenger levels, and has reached three semifinals on the
ATP Tour. He suffered a serious shoulder injury in 2003, which after multiple surgery kept him out of competition for almost a year. After returning from injury in 2004, he had dropped in the rankings to World No. 846 on 24 May. Subsequently, he has gradually climbed the rankings, and after successful performances at the Challenger level in autumn 2006, he entered the Top 100 again. In January 2007, he continued his good performances as he defeated World No. 8
David Nalbandian in three sets in the first round of
Chennai Open. This was Pless' first win against a Top-10 ranked player. In 2007 he also managed to take a set from tennis legend
Roger Federer at their meeting in Dubai, but eventually Federer won the tie 7–6(2), 3–6, 6–3. It was first set Federer had lost that year after he had won the Australian Open without losing a single set. In 2008 he reached two Challenger finals (in Izmir, Turkey and Rimouski, Canada), but ended the year outside of Top 100. 2009 was his last year on tour. ==Junior Grand Slam finals==