Sullivan previously served as the Giants' wide receivers coach, before moving to quarterbacks coach in 2010. His coaching was cited as a major reason for Eli Manning's success in 2010. Manning set franchise records with 339 completions and a 62.9 completion percentage, as well as his second season with over 4,000 yards, but also threw a career-high 25 interceptions.
On February 10, 2012 Sullivan was hired as the Tampa Bay Buccaneers offensive coordinator. On December 31, 2012, NFL.com reported that Sullivan will be interviewed by the Chicago Bears for the head coaching position after Lovie Smith was fired.