Cardiff are 10 points ahead of second-placed Leicester City.
Martin O’Neill: “There were a few teams interested in Fraizer and his contract was up at the end of the season, so this is a chance for him to play pretty regularly.
“It’s also an opportunity to help Cardiff into the Barclays Premier League.
“At the moment they’re [doing well], although those can be eroded as we all know.
"That said, they are in a great position.
“Fraizer has signed a three-and-a-half-year contract and has all the motivation in the world to get back into the Barclays Premier League.”
Sunderland FixturesTuesday January 29 19:45 Sunderland v Swansea City Saturday February 2 15:00 Reading v Sunderland Saturday February 9 15:00 Sunderland v Arsenal Saturday February 23 15:00 West Brom Sunderland Saturday March 2 15:00 Sunderland v Fulham Saturday March 9 15:00 QPR v Sunderland