NFL: DEC 29 Titans at Texans
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For the past 53 years, George Halas has held the record as the oldest person to ever serve as a head coach in an NFL game, but that's going to change on Sunday when the Texans host the Jaguars. After firing Bill O'Brien on Monday, the Texans decided to replace him with interim coach Romeo Crennel, which is notable because it's Crennel who's going to break the record. 

When Houston's Week 5 games kicks off, Crennel is going to be 73 years and 112 days old, which means he's officially going to become the oldest head coach in NFL history. 

The current record is held by Halas, who was 72 years and 318 days old when he coached the final game of his career in December 1967. To put into perspective how rare it is to see a coach of Crennel's age on the sideline, just consider this: Since Halas' retirement, there has only been one coach who even came remotely close to catching him and that was Marv Levy, who was roughly eight months away from turning 73 when he coached his final game with the Buffalo Bills in December 1997. 

Although he's only been on the job for a few days, it looks like the 73-year-old Crennel is already starting to fit in with the younger guys in Houston. 

The fact that Crennel is going to make his way into the NFL record book is somewhat surprising, and that's only because it almost didn't happen. Back in January, Crennel contemplated retirement, but instead of calling it quits he decided to return to Houston for one more season as an assistant head coach on the team. 

Crennel has been coaching in the NFL since 1981 when the Giants hired him as a special teams coach. Since then, he's also coached with the Patriots, Jets, Browns and Chiefs. The Texans are the third team where Crennel has been the head coach, along with Kansas City and Cleveland. 

Once Crennel officially gets the age record, it will almost certainly be a few years before anyone passes him -- and that's if anyone passes him at all. If Crennel serves as interim coach for the entire year, that means he'll be 73 years and 199 days old when the Texans play in their regular season finale. 

The coach with the best chance to eventually pass him is probably Pete Carroll, who just turned 69 in September. However, for that to happen, Carroll would have to coach until September 2025, when he'd be 74 years old (due to his birthday, Carroll wouldn't be able to break the record as a 73-year-old in 2024).

Patriots coach Bill Belichick could also end up passing Crennel. Belichick just turned 68 and would have to coach until at least 2025 to pass Crennel, and he'd only be able to get the age record if Carroll decides to retire. 

Also, since you're now probably wondering, here's a look at the age of the 10 oldest active head coaches in the NFL. 

NFL's 10 oldest coaches

1. Texans interim coach Romeo Crennel, 73 (turns 74 on June 18, 2021)
2. Seahawks coach Pete Carroll, 69 (turns 70 on Sept. 15, 2021)
3. Patriots coach Bill Belichick, 68 (turns 69 on April 16, 2021)
4. Buccaneers coach Bruce Arians, 68 (turns 69 on Oct. 3, 2021)
5. Vikings coach Mike Zimmer, 64 (turns 65 on June 5, 2021)
6. Chiefs coach Andy Reid, 62 (turns 63 on March 19, 2021)
7. Broncos coach Vic Fangio, 62 (turns 63 on August 22, 2021)
8. Washington coach Ron Rivera, 58 (turns 59 on January 7, 2021)
9. Ravens coach John Harbaugh, 58 (turns 59 on September 23, 2021)
10. Raiders Jon Gruden, 57 (turns 58 on August 17, 2021)