Tommy Haas and John Isner will return to the Heineken Open in January.
Haas is ranked 12th in the world and reached the quarter-finals this year, while 13th ranked Isner won the title in 2010.
Already confirmed for the tournament is four-time Heineken Open champion David Ferrer and French entertainer Gael Monfils.
Ferrer is the current world number four has had another consistent season and made his first grand slam final in the French Open in June.
If Ferrer claims the 2014 title, he will surpass the feats of Australian legend Roy Emerson in the 1960's, to become the greatest ever champion at the Heineken Open.
Former French number one Monfils is a quarter-finalist at three of the four grand slams and thrilled earlier this year when he made the semi-finals in Auckland.