He achieved his greatest professional success as the starting quarterback of the Baltimore Ravens during their Super Bowl-winning season in 2000.
Dilfer played college football for the Fresno State Bulldogs, winning the Sammy Baugh Trophy as a junior, and was selected sixth overall by the Tampa Bay Buccaneers in the 1994 NFL draft.
He spent his first six seasons with Tampa Bay, earning Pro Bowl honors in 1997, but was released due to inconsistent play.
His next four seasons were spent primarily as a backup with the Seattle Seahawks and he had short stints with the Cleveland Browns and the San Francisco 49ers before retiring in 2008.
Dilfer helped Fresno State win or share the conference title for three straight seasons and started in two bowl games.
In his junior season, Dilfer led the nation in pass efficiency en route to being named the WAC Offensive Player of the Year.
He also set the NCAA record for consecutive pass attempts without an interception (271) that stood until 2007, when Kentucky quarterback Andre' Woodson broke it.
The following season, a year that Tampa's offense was aided by the arrival of rookie Warrick Dunn and the emergence of Mike Alstott, Dilfer was the first Tampa Bay quarterback to ever go to the Pro Bowl, which some say was a reward for a highly efficient season in the Buccaneers' limited offense.
During the playoffs, Dilfer went 3–0, and the Ravens advanced to Super Bowl XXXV in Tampa, Florida to meet the New York Giants.
The Ravens won their first Super Bowl title in a 34–7 blowout, which saw Dilfer complete 12 of 25 passes for 153 yards and one touchdown.
Although one of Dilfer's passes was intercepted by linebacker Jessie Armstead and returned for a touchdown, the play was negated due to a holding penalty against the Giants.
Dilfer acknowledged that he still felt bitter about the Ravens moving on from him in a 2021 interview, noting he played through injury during the season, most notably in his shoulder alongside osteitis pubis, an inflammation near the pubic bone and hip flexor muscle.
On October 28, 2002, in Week 8, he suffered a season-ending torn Achilles tendon against the Dallas Cowboys on the synthetic turf at Texas Stadium.
In March 2005, Dilfer was traded to the Cleveland Browns where it was hoped he would mentor rookie quarterback Charlie Frye.
In his lone season for the Browns, Dilfer passed for 2,321 yards and 11 touchdowns, throwing 12 interceptions and fumbling 9 times (losing 7 of those).
In May 2006, Dilfer was traded to the San Francisco 49ers, this time to serve as a mentor to the 2005 first round draft pick Alex Smith.
However, with Smith's effectiveness in question coming back from injury, coach Mike Nolan announced on November 14, 2007, that Dilfer would be the starting quarterback.
Although he had suffered an Achilles tendon injury playing basketball earlier in the off-season with his wife, Dilfer stated that he was planning to retire anyway.
He joined Brad Nessler to call the second game of the network's Monday Night Football doubleheader on September 13 of that year.
In 2021, the Mustangs finished 13–1, including one win by forfeit, and defeated Christ Presbyterian Academy, 27–0, in the Division II Class AA State Championship game.
In 2022, the Mustangs finished 13-0 and again defeated Christ Presbyterian Academy with a score of 42–0 to win their second straight Division II Class AA State Championship.
[27] On June 2, 2003, Dilfer made his first public comments regarding his family's loss and, still grieving, openly wept.
[28] On a broadcast of the Cardinals and Titans preseason game in 2012, Dilfer admitted he weighed 265 lbs and was drinking himself to sleep during his tenure with the Seahawks.