Blackwell attended Richland High School. He accepted a football scholarship from Texas Christian University. As a freshman, he was named the starter at tight end and appeared in 11 games. He collected 20 receptions (second on the team), 172 receiving yards (third on the team) and no touchdowns.
As a sophomore, he appeared in 8 games, tallying 33 receptions (second on the team), 389 receiving yards (third on the team) and 2 receiving touchdowns (second on the team).
As a junior, he appeared in 11 games, registering 64 receptions (school record), 832 receiving yards (third in school history) and 5 receiving touchdowns (tied for second on the team). He tied for third all-time in receptions in a single-game with 12 catches against the University of Missouri.[1]
As a senior, he appeared in 9 games, leading the team with 64 receptions (tied his school record) for 762 yards (eighth in school history) and 6 touchdowns. He had 11 receptions against the University of Houston to set an NCAA record for most career receptions by a tight end.[2] He was named to the All-America Team.[3] He finished his career with 181 receptions (school record), 2,155 receiving yards (fourth in school history) and 13 receiving touchdowns (third in school history).[4]
In 2001, he was inducted into the TCU Lettermen's Association Hall of Fame.[1]
On December 30, 1993, he signed as a free agent with the Los Angeles Rams.[7] On June 1, 1994, he was released before the start of the season.[8]
In June 1994, he signed with the Fort Worth Cavalry of the Arena Football League.[9] He was a two-way player at fullback and linebacker. He registered 2 receptions for 18 yards, 17 carries for 46 yards, 13 tackles, 3 sacks, one fumble recovery and one blocked kick.