The 28-year-old has penned a five-year deal with the French club and is looking forward to a fresh challenge, after slipping down the pecking order at Roma.
The arrivals of Javier Pastore, Bryan Cristante and Steven N'Zonzi meant the Dutch international was surplus to requirements but he does not believe a move to Marseille is a step down.
"It's true that Olympique Marseille have not played in the Champions League for a long time and I have played in the Champions League with AS Roma in recent years but you cannot base the choice of your future on whether on not you will play in the Champions League," he said.
"When you have a chance to sign for a club your own personal feeling is very important. When a club demonstrates that they really want you to sign for them and wants to do everything in their power to sign you from a Champions League club that tells it's own story.
"Olympique Marseille is a great challenge and in terms of the Dutch national team the manager Ronald Koeman has been clear that if a player is playing well at his club there is a chance to play for the national team.
"I just want to focus on my first match for Olympique Marseille against AS Monaco and then we will see what will happens in regards to the Dutch national team."