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.
"Billís not only a good friend, but a guy that Iíve admired in the way he handles himself," Shanahan told me at Lucas Oil Stadium. "And what heís been able since heís been in New England has been off the charts, and Iíve always studied everything heís done. ... It really goes back before we were head coaches to when we were assistants. It goes back to games donít realize where as coordinators youíre 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.
"Thereís no question about it," he said. "Thatís what keeps you in the game."