Mario Ancic says he has retired from professional tennis because his body would not allow him "to continue on a high level."
The 26-year-old Croat said Wednesday it was "one of the toughest decisions I ever had to make."
Ancic first came to prominence in 2002 in his Grand Slam debut at Wimbledon, where he defeated seventh-seeded Roger Federer in the opening round.
Ancic reached a career-high ranking of No. 7 in 2006, two years after he reached the Wimbledon semifinals for his best Grand Slam result.
However, he suffered from mononucleosis in 2007 and lately has struggled with a back injury.