As a senior, he broke Pat Haden's state record for touchdown passes in a season with 35 and received Northern California offensive player of the year honors.
Sweeney accepted a scholarship from Fresno State University to be coached by his father and replace at quarterback the graduated Jeff Tedford.
As a senior, he had the lowest interception percentage (2.37) among the top 25 rated passers and set a conference mark with a career-high 4 touchdown passes against New Mexico State University.
[9] In his first game against the New York Jets, he became the third ever rookie quarterback to start for the Cowboys, following Don Meredith (1960) and Roger Staubach (1969).
[12] The next game, he was given the opportunity to start against the Minnesota Vikings, but lost 43–3 after completing just 10 of 28 passes for 93 yards, with 2 interceptions and 2 fumbles.
[13] In 1989, with the arrival of new head coach Jimmy Johnson and with the team also intending to draft a quarterback, he was left unprotected in Plan B free agency.
[15] In 1991, he signed with the Montreal Machine of the World League of American Football, where he was named the starter at quarterback, before being passed on the depth chart by Michael Proctor.