The former world No.2 Tommy Haas and fellow German and 2008 champion Philipp Kohlschreiber will play in th Heineken Open men's tennis tournament in Auckland in the New Year.
2009 finalist Sam Querrey and former world No.8 Jurgen Melzer were also confirmed as the final field was announced.
There are now seven top 30 players in the field.
Haas was recently named ATP comeback player of the year as he rocketed from outside the top 200 to reach a ranking of 21, while Kohlschreiber has had his best season yet.
After making the semi-finals in Auckland, Kohlschreiber went on to his fourth tour title in Munich, made the quarter-finals at Wimbledon and reached a career-high ranking of 16.
Heineken Open Tournament Director Karl Budge says he's excited about the number of players coming to Auckland who are in some of the best form of their careers, including defending champion David Ferrer.
Ferrer won seven titles this year, more than any other player on the ATP Tour - including his debut Masters crown in Paris.
The 2013 Heineken Open field has a cut-off at a world ranking of 61, and includes players from 14 nations.