He was originally drafted by the Houston Texans in the second round of the 2002 NFL Draft and played four seasons with the team. In 2006 Gaffney became a free agent with the Patriots.
In his first-ever playoff game, on January 7, 2007, against the New York Jets, Gaffney had a near-career day, catching eight passes for 104 yards, his second 100-yard performance as a receiver (in 10 regular season games, Gaffney caught 11 passes for 142 yards and one touchdown). Gaffney followed that performance a week later against San Diego with another 100-yard game, in which he caught 10 passes and scored a touchdown.
On the whole in his career, he has caught 218 passes for 2,600 yards and 13 touchdowns.