Westwood's former boss when he was at Carlisle, Paul Simpson, has backed the 26-year-old to be a success at the Stadium of Light.
He told The Journal: "Keiren was certain in his mind what he wanted to do and he deserves it for achieving a move to a Premier League club.
"He was strong enough to deal with his contract situation and still perform, even though there was so much going on.
"He looked a real quality keeper at Championship level and joining a Premier League club is a natural progression for him. I think he will become a top-class international keeper.
"He has all the tools to make it in the Premier League, no doubt about it. It isn't a gamble by Sunderland, because he won't let them down."