665. In June, he played his first ATP tournament at Rosmalen, losing in the first round against Juan Carlos Ferrero. In September, he made his debut for the Dutch Davis Cup team in the World Group Play-offs against the Czech Republic, losing against Tomáš Berdych in straight sets and winning over Jan Hernych after the competition already was decided. In November, Haase won his first Challenger tournament in Nashville, beating two top-100 players in the process. In December, he won his first Masters title by beating defending champion Raemon Sluiter in the finals of the 2006 Sky Radio Tennis Masters. Haase further reached three semifinals on the ATP Challenger Tour and ended the year ranked no. 164. 2007
In March, he won his second Challenger in Wolfsburg. In July, Haase reached his first ATP Tour semifinal at the Dutch Open in Amersfoort, where in the quarterfinals. he beat a top-100 player Florent Serra.
665. In June, they played their first ATP tournament at Rosmalen, losing in the first round against Juan Carlos Ferrero. In September, they made their debut for the Dutch Davis Cup team in the World Group Play-offs against the Czech Republic, losing against Tomáš Berdych in straight sets and winning over Jan Hernych after the competition had already been decided. In November, Haase won their first Challenger tournament in Nashville, beating two top-100 players in the process. In December, they won their first Masters title by beating defending champion Raemon Sluiter in the finals of the 2006 Sky Radio Tennis Masters. Haase also made three semifinals on the ATP Challenger Tour and finished the year ranked 164th.

2007
In March, they won their second Challenger in Wolfsburg. In July, Haase reached their first ATP Tour semifinal at the Dutch Open in Amersfoort, where in the quarterfinals they beat top-100 player Florent Serra.