Crennel has been O'Brien's defensive coordinator and assistant head coach over the last six years. The 73-year-old was appointed as interim head coach when O'Brien was fired on Monday.
In Crennel, the Texans are getting someone, like O'Brien, who has spent time under Bill Bellichick's New England Patriots system and has helped win Super Bowls.
The defensive guru is also no stranger to being a head coach after already manning the sidelines in Cleveland and Kansas City.
What should give the Texans pause is Crennel's record in that role. He is 28-55.
Here are facts and career highlights of Crennel as he heads into his first Texans game as head coach this Sunday against Jacksonville:
- He's a five-time Super Bowl champion: Crennel got his first taste of championship glory with the New York Giants, with whom he won rings after the 1986 and 1990 seasons. He coached special teams and, later, the defensive line for the "G-Men." Of course, he's best known for his time in New England, where he was part of three Super Bowl-winning teams as defensive coordinator between 2001 and 2005. His Super Bowl XXXIV win happened in Houston.
- He never played in the NFL: Crennel is arguably an intimidating presence on the sideline, which one would assume comes from years and years in the league. But he has never stepped foot on a playing field as a pro football player. However, he played collegiate football for Western Kentucky as a defensive lineman for nearly his entire time there.
- His deal with the Texans was among the highest in the NFL: O'Brien was able to lure Crennel to Houston at a big price. Crennel signed a three-year contract at about $1.8 million a year, making him, at the time, one of the highest paid defensive coordinators in the league.
- He coached the Browns to a winning record: Yes, those Browns. He spent a total of four seasons as the head coach in Cleveland. The highlight of his time there was in 2007 when the Browns went 10-6, marking just the second time they finished with a winning record since they came back to the NFL in 1999. That season won him a contract extension.
- He was out of football in 2009: Crennel spent a year after he was let go in Cleveland to have hip replacement surgery, forcing him to sit out the entire 2009 season.
- He witnessed his own player's death: In 2012, during his final season as head coach of the Kansas City Chiefs, Crennel tried to stop linebacker Jovan Belcher from committing suicide. Belcher, who was suspected in the murder of his girlfriend, died of a self-inflicted gunshot wound at the team's training facility.