Oscar says he didn't think twice when Chelsea came calling.
He said: "When my agent told me that Chelsea were interested it was not something I even needed to think about.
"They are the champions of Europe, but they are still showing so much ambition by improving the squad. To win the European Cup and still sign guys like myself and Eden Hazard shows you the ambition the owner and manager have.
"With the squad we have I will be looking at winning the Premier League title and also the Champions League.