Auckland - David Ferrer became the third seeded player to pull out of this week's Auckland Open when he withdrew on the eve of the tournament Sunday citing a back injury.
Top-seeded Ferrer, the world number 10 and a four-time winner in Auckland, told tournament organisers he suffered the injury in Doha where he beat Tomas Berdych in the Qatar Open final on Saturday.
Defending champion John Isner and Gael Monfils were also late withdrawals from the Auckland tournament, a final warm-up for the Australian Open which begins on January 19.
Tournament director Karl Budge said he believed Ferrer would have played in Auckland if he had felt able.
"He doesn't have a record of pulling out of events and he wouldn't be doing so if it wasn't absolutely necessary this time around," Budge said.
World number 13 Ernests Gulbis takes over as the top seed in a field which includes three other top 20 players - Roberto Bautista Agut (15), Kevin Anderson (16) and Tommy Robredo (17).
Gulbis rose to prominence at Roland Garros last year when the Latvian upset Roger Federer in the fourth round of the French Open.
Isner pulled out of Auckland after declaring himself tired from playing in the Hopman Cup final in Perth on Saturday.
Frenchman Monfils, who has now pulled out late from Auckland two years in a row, said he was unavailable for personal reasons.