The 30-year-old told Autosport: "I was ahead of [Di Resta]. I was ahead of him in the championship. I was ninth, he was 13th. That's the bottom line. What more can I say?
"I know he's a strong driver, but I have shown I am a strong driver too. It's nothing I have to be worried about.
"I don't think about problems. I look forward to races. I'm a positive person. If I only look at potential problems, then I'll get myself into a real problem. I've only been out of racing for one year."
Sutil was second fastest in this morning's session at the final pre-season test event in Barcelona.