Houston Texans head coach Bill O'BrienBill Belichick has had quite a few assistant coaches through his 20-plus years as a head coach, but few have risen through the ranks.

The New England Patriots head coach will go up against one of those assistants Sunday in Houston Texans coach Bill O'Brien, who's in his second season leading the team. Belichick also will meet a few other old friends in Texans defensive coordinator Romeo Crennel, linebackers coach Mike Vrabel and a few more.

But O'Brien is one of just seven assistants on Belichick's coaching tree to go on to become a head coach.

Crennel also is a part of that small group, and so are some other big names like Alabama football coach Nick Saban and Patriots offensive coordinator Josh McDaniels. But overall, Belichick's assistants haven't had much success in bigger roles in the NFL.

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