Germany's Tommy Haas has decided not to defend his AAPT Championships hardcourt title, turning down a wild card for the tournament which starts in Adelaide, Australia on Monday.
Haas gave no reason for his decision.
The 23-year-old captured his second career title by defeating Chile's Nicolas Massu in the Adelaide final at the start of this year.
Haas has won three other ATP titles since then -- in New York in late August and in Austria and Germany in October.
Pete Sampras has accepted a wild-card entry to the tournament to prepare for the Australian Open. Sampras has never played in the event.
Mark Philippoussis also was offered a wild-card slot, while No. 1 Lleyton Hewitt will skip the tournament. Hewitt has played in it every year since winning it in 1998.
Tim Henman, Marcelo Rios, Nicolas Kiefer and Thomas Enqvist will play in the AAPT Championships.
The Australian Open is Jan. 14-27 in Melbourne.
Sampras will be looking to win his first tournament since 2000 and end a poor run of form which has seen him drop to 10th in the world, his lowest ranking since 1989.
Tournament director Colin Stubs attributes Sampras' decision to play in the event to his recently appointed coach Tom Gullikson, the Australian Associated Press reported.
"Gullikson's a bit of a taskmaster and he's probably said to him, 'listen Pete, you always come down to Australia a little bit underdone,' " Stubs said. "He hasn't been all that successful in the Australian Open over the last few years."
Sampras joined forces with Gullikson, a former U.S. Davis Cup captain, last week after parting with his coach of seven years Paul Annacone, who he dismissed last month.