He said: "I don't know anything about a transfer to Rangers. I have heard the stories in the media, but I have not been approached.
"My contract in Bremen finishes in the summer and I'm looking at every option to see what happens. I don't know what my future will be, whether I stay in Werder or not, I'm not sure. Rangers are a good team and both them and Celtic have done well in Europe over the past couple of years. We'll see what happens and, if I get an offer from them, we can talk about it.
"But there's no doubt Scottish football is becoming stronger," he added. "Scotland played well in the qualifying for Euro 2008, the only mistake they made was against Italy in the last game.
"I think they can go on and build on that success to reach the World Cup in 2010."