"I have a tremendous amount of respect and admiration for Romeo, both personally and professionally," Chiefs Chairman and CEO Clark Hunt said in a
statement on the team's website. "He is an accomplished coach, a man of great character and he helped guide our football team through some extremely challenging circumstances this season."
But Hunt said he's "embarrassed by the poor product we gave our fans this season" and the only choice is to move the franchise in a different direction.
Crennel finished his tenure in Kansas City at 3-15 and is 28-55 overall as an NFL head coach.
"Obviously I'm very disappointed in the way our season went," Crennel said in a statement released by the team Friday afternoon. "At the end of the day, the NFL is a performance-based league, and we weren't able to win.
"I want to thank the Hunt family for the opportunity as well as our players, coaches and fans for their support during my time in Kansas City. As for my future, I'm planning to take some time to reflect on this season, evaluate everything, and make a decision based on what's right for myself and my family."
The move comes after a tumultuous season whose only wins were an overtime thriller in New Orleans and a convincing victory over Carolina the day after Chiefs linebacker Jovan Belcher killed his girlfriend in their home and then killed himself in the Arrowhead Stadium training facility parking lot.
Crennel, who witnessed Belcher's suicide along with Pioli and defensive coordinator Gary Gibbs, joined the team as defensive coordinator in 2011. He was named the interim head coach when Todd Haley was fired with three games remaining in the 2011 season. The interim was removed from his job title prior to this year.
Crennel barely made it through a season of heavy fan scrutiny that included fears of local television blackouts, a viral social media gaffe and the flying of banners calling for his and Pioli's ouster over Arrowhead Stadium on Sunday game days.
Known as a top-level coordinator in the NFL, his head-coaching abilities have come under fire as the Chiefs' struggles mounted in 2012.
The Chiefs' inept offense managed 18 touchdowns in 16 games, finished minus-24 in turnover ratio and lost nine times by two touchdowns or more. Along the way, they broke an 83-year-old NFL record by not holding a lead in regulation until their ninth game.
Crennel seemed to know the end was coming Sunday night when he was asked to defend his job and said, "If your criteria is wins and losses, there's not much defense."
Crennel remained the team's defensive coordinator for the first eight games of this season, but stepped down and handed over the defensive reigns to Gibbs, who had been serving as the linebackers coach.
Crennel has spent 31 years in the NFL. Before coming to Kansas City, he was the head coach in Cleveland from 2005 to 2008.
Crennel first teamed up with Pioli in New York in 1997 when Crennel was named the defensive line coach and Pioli the Director of Pro Personnel.
The two teamed up again in 2001, the second of a seven-year stint for Pioli in New England, when Crennel was named the defensive coordinator.
Crennel began his NFL coaching career as a special teams/defensive assistant coach with the New York Giants in 1981.
Kansas City will have the No. 1 pick in the draft after the most disappointing season in its 53-year history. The only other time the Chiefs finished 2-14 was 2008, the year before Pioli was hired. They were 2-12 in 1977, the only other time they've failed to win at least three games.