The 29-year-old goalkeeper has moved to Hillsborough on a free transfer after making just 19 appearances for the Black Cats.
After missing the final six months of last season with a shoulder injury, Westwood says that he is keen to get his career back on track with the Owls.
"I started last season as number one. That was fantastic for myself. I played a few games, got injured and that was a real setback for me," he told the Sunderland Echo.
"Sunderland is a fantastic club with great people. I've got good friends there. But I'm 29 and I want to be playing games. I can't be sitting on the bench. Obviously, playing football is your bread and butter.
"The injury was a setback for myself. I could have gone on and played 30 odd games for Sunderland last season, but I didn't. But I feel stronger than ever now."
Westwood has signed a two-year deal with Wednesday.