Coaching Tom Brady might sound like an easy job -- you call a play, Brady runs it to perfection and then you look brilliant -- but apparently, coaching Brady is actually much more difficult than that thanks to to the quarterback's obsession with football.  

During a recent interview with CBS Sports Radio 610 in Houston, Texans coach Bill O'Brien, who spent five seasons with the Patriots (2007-11), explained why coaching Brady can be such a demanding job. 

Apparently, the biggest issue with coaching Brady is that you have to be on call 24/7 because that's how often Brady is thinking about football. 

"One of the most difficult jobs you can have is coaching Tom because he wants to be coached, you coach him every single day, every minute of the day and all year round because he's all football," O'Brien said. 

Apparently, it's not easy to coach Tom Brady.  USATSI

In the world of football, some guys are hard to coach because they don't care about football. Not Brady, though, he's the exact opposite. 

"He's a phenomenal guy and the reason why he is what he is, is because he's obsessed with football," O'Brien said. "He's a great family guy, don't get me wrong, but he's obsessed with football and so when you're coaching him you better be ready to go at a moment's notice whether it's for a meeting or practice or game and it made me a much better coach when I was fortunate enough to coach him."

I'm guessing we'll never hear O'Brien say any of this about Brock Osweiler

Brady's football obsession is so legendary that O'Brien has regular conversations about it with current Patriots offensive coordinator Josh McDaniels. 

"Josh McDaniels is one of my closest friends and we talk about this all the time," O'Brien said. 

O'Brien served as the Patriots' quarterback coach in 2009 and 2010 before being promoted to offensive coordinator in 2011. 

The Texans coach left New England after the 2011 season to take the head coaching job with Penn State, and that's when he realized how important it is to have a player who obsesses over football like Brady. 

"When I went to Penn State after having coached Tom (Brady) for a few years that was my first eye opener," O'Brien said. "We went out for out first spring practice at Penn State and I was like, alright we're going to do these 100 plays today and I think we were like 1-for-30. Now, there was a high wind that day in Happy Valley so I blame it on the wind, but guys didn't know where to line up and it was like, what am I doing? So we simplified it and began being decent offensively that first year, but that was my first experience of knowing it's different."

In a twist of fate, O'Brien will be coaching another Tom this season in Houston, and O'Brien sounds pretty impressed with Tom Savage, the current front-runner to win the Texans' starting quarterback job. 

"Tom [Savage] is a great guy to coach, he's into it, he loves it, he's passionate about it, he has a good command for what we're doing and he's ahead because he has been here," O'Brien said. 

If Savage is half as obsessive as Brady is about football, then the Texans might actually be in good hands this year. 

(Wink of the CBS Eye to USA Today's Patriots Wire)