DeBerg led his team to a Pacific Coast Athletic Association (Big West Conference) title, and was named the PCAA offensive player of the year.
Although large portions of his professional career were spent as a backup, DeBerg accumulated significant NFL statistics (particularly during the early 1990s, when he was the starting quarterback for the Kansas City Chiefs).
DeBerg played for the San Francisco 49ers (1978–1980), Denver Broncos (1981–1983), Tampa Bay Buccaneers (1984–1987, 1992, 1993), Kansas City Chiefs (1988–1991), Miami Dolphins (1993), and Atlanta Falcons (1998).
He was selected by the Dallas Cowboys in the tenth round (275th overall) of the 1977 NFL draft, but was waived before the start of the season when he could not displace fellow rookie quarterback Glenn Carano.
DeBerg threw all but 24 passes thrown by a quarterback for the 49ers that season, which included 15 starts and one appearance replacing Montana as a starter.
[6] DeBerg would start nine of the first twelve games of the 1980 season but was eventually supplanted by Montana as the permanent starter; notably, DeBerg started the first three games of the season with an unusual device born out of necessity: with damaged vocal cords from a hit to the neck during the preseason that left him unable to speak above a whisper, DeBerg would have a speaker, amplifier, and power pack attached to the back of his shoulder pads (with a switch in his helmet and a mini microphone on the bar of his facemask) to call signals and audibles.
[9] DeBerg was traded to the Denver Broncos on August 31, 1981 for a 1983 fourth-round draft pick (#87, Chuck Nelson),[10] rejoining Dan Reeves (who coached him during his short time with the Cowboys).
DeBerg was the second-string quarterback behind Craig Morton, making spot appearances while having one start against Cincinnnati in the twelfth week of the season.
Against Seattle, he threw just 10-of-20 before suffering a shoulder injury that knocked him out of the game and as it turned out the remainder of the regular season.
After the season, DeBerg was traded to the Tampa Bay Buccaneers and eventually signed a four-year contract worth $2.5 million.
[15] DeBerg was the central starter for the 1984 Buccaneers, who posted one of the league's more productive offensive attacks when he was the starting quarterback.
The Bucs earned their first win of the season with DeBerg coming off the bench, a 21–17 victory against Detroit on September 16 in which he completed 18 of 27 passes (66.7 percent) for 195 yards with two touchdowns and no interceptions.
On March 31, 1988, The Buccaneers traded him to the Kansas City Chiefs for safety Mark Robinson and fourth- (#86, John Bruhin) and eighth-round picks (#198, Anthony Simpson).
He seriously injured his non-throwing hand in a loss to the Houston Oilers on December 16, which required the insertion of a pin into his broken finger to keep it straight.
For their last two games and the playoffs, the Chiefs ran their offense out of the shotgun formation to protect DeBerg from having the football jammed in his injured hand during the center-to-quarterback exchange.
Kansas City won those games to clinch their second playoff appearance in over a decade, with DeBerg completing 44 of 59 passes for 527 yards with two touchdowns and no interceptions.
In a 17–16 loss to the Miami Dolphins in the 1990 AFC wild-card game, he completed 17 of 30 pass attempts for 269 yards with one touchdown and one interception.
[18] He was inactive for the Week 11 matchup for Miami before being tapped to start the next week against New England due to injury to Scott Mitchell, who had become the starter when Dan Marino had ruptured his Achilles tendon in October before Mitchell dislocated his left throwing shoulder that left only Doug Pederson in the QB room.
However, it was the only win in his four starts (three of the games saw him throw two interceptions each), one of which saw him leave briefly after a hit saw him bleed from a helmet shot to his chin that required seven stitches to go along with a bandage covering his throat before he returned to play after halftime.
[20][21] DeBerg returned to the NFL in 1998 at age 44, rejoining head coach Dan Reeves as a backup with the Atlanta Falcons.
[22] On October 25, with Chris Chandler unable to play, Deberg became the oldest quarterback to start in an NFL game when he led the Falcons against the New York Jets.
On February 5, 2010, DeBerg was inducted into the Rebel Hall of Fame at Savanna High School for his achievements as a starting quarterback in college and the NFL.
[26] DeBerg was head coach of the Arena Football League's Indiana Firebirds in 2004 for five games; the team's record during his tenure was 0–5.