But the truth is they matched wits last summer, when Belichick invited Shanahan and right-hand man Bob Slowik (now his secondary coach in D.C.) in for a training-camp visit. It's not unusual for other coaches to come through camp -- you see plenty of college guys doing it -- but Shanahan's brief sojourn from coaching allowed him an opportunity he most certainly wouldn't have had otherwise.
As fort the specifics of that day in Foxborough, Shanahan's tight-lipped on the details, not wanting to spill his own guts or violate anyone's trust. But he would allow that the experience was valuable as he goes into his third head-coaching stint.
"Bill’s not only a good friend, but a guy that I’ve admired in the way he handles himself," Shanahan told me at Lucas Oil Stadium. "And what he’s been able since he’s been in New England has been off the charts, and I’ve always studied everything he’s done. ... It really goes back before we were head coaches to when we were assistants. It goes back to games don’t realize where as coordinators you’re going against each other. You watch what they do over the years, different organizations, different personnel, how they find different ways to win."
As for the difference it makes, Shanahan agreed that the two have pushed each other over the years, and this was another example.
"There’s no question about it," he said. "That’s what keeps you in the game."