He said: "Many people think that coming here may be an error and perhaps they are right. But when we win a trophy, I'll know it was the right decision.
"Choosing a club that isn't in Europe may have surprised some people but we want to be in the Champions League next season. That's our motivation."
He explained he had moved to the Ligue 1 side "for a number of reasons".
"The president and his coaching staff have the same ambition as me, which is to reach the top of European football," he said.
"They assured me that I was as a fundamental part of this project, which gave me confidence and security.
"This club wants to win trophies and that, together with the role I'll have in the team, made me want to come here."