De Bakker received a wild card into the ATP Amersfoort event in July 2006 and defeated top 100 and French Open Quarterfinalist Julien Benneteau in the 1st round, winning in straight sets 6–3, 6–3. In the 2nd round he faced Frenchman Marc Gicquel and lost in 3 sets. As he was the reigning Junior Champion, De Bakker received a wild card into the main draw of the 2007 Wimbledon Championships, where he would lose in 5 tight sets to qualifier Wayne Arthurs.
In October 2006, De Bakker won his first senior international title in a Futures event in Albufeira, Portugal, where he beat Briton Morgan Phillips in the final. This was followed by another win in a Futures tournament two weeks later in San Miguel, Portugal. He reached a career high ATP ranking of 228 on 25 August 2008.
On 22 March 2009, he finished as runner-up in the Caltanissetta Challenger tournament to compatriot Jesse Huta Galung, losing in straight sets. On 5 May 2009, as a qualifier and ranked 236, he defeated the 5th seed Rainer Schüttler in the first round of the BMW Open in Münich in straight sets, before losing to former world number one, Lleyton Hewitt. De Bakker would follow this up in the 2009 Ordina Open, by qualifying for the tournament and losing in the second round to Rainer Schüttler, after defeating Björn Phau in three tight sets. De Bakker hit a rich vein of form in the month of August, winning four Challenger tournaments, and bumping his ranking from 256 to 122, in the span of one month. His form continued in Davis Cup competition, by beating World Number 13 Gaël Monfils in 4 sets, and putting the Netherlands up 1–0 on France, but lost to Jo-Wilfried Tsonga in four tight sets. De Bakker would finish the year ranked 96th.
De Bakker started 2010 in much the same way he finished 2009. He reached the quarter-finals of the 2010 Aircel Chennai Open, after defeating the eighth seed, Rajeev Ram, and compatriot Robin Haase, he lost to Janko Tipsarević. This would boost his ranking to number 81 in the world, and gave him a high enough ranking to receive direct entrance into the 2010 Australian Open – Men's Singles. In his first Grand Slam in three years, the Dutchman was paired up against the 6th seed Andy Roddick. After losing the first set, de Bakker lost the second and third set by one break each.
De Bakker's next tournament was his first ever Masters event, the 2010 BNP Paribas Open in Indian Wells. He started off winning his opening match against Marcos Daniel in straight sets, before advancing to the third round after beating 30th seed Janko Tipsarević where he retired just after five games of play at 3–2 first set. In the third round, he fell to eventual finalist Andy Roddick. De Bakker played his second Masters event two weeks later the 2010 Sony Ericsson Open, winning his first round match against Rajeev Ram in straight sets, before falling again to the eventual finalist, this time Tomáš Berdych with the same scoreline as in Indian Wells.