It's the end of an era for football's coaching icons, and it may mark a shift in what makes a great coach

• Three of football's top coaches — Bill Belichick, Nick Saban, and Pete Carroll — left their longtime roles.
• Saban is set to retire, while Belichick and Carroll may search for new homes in the NFL.
• The trio's shake-up marks the end of an era — and may indicate a shift in what makes a great coach.

The highest levels of football have reached the end of an era.

Three of the sport's most successful coaches — Bill Belichick of the New England Patriots, Nick Saban of the Alabama Crimson Tide, and Pete Carroll of the Seattle Seahawks — have vacated the head coaching positions they've held for more than 50 years combined. Reporting suggests that Saban is set to retire from coaching altogether, while Belichick and Carroll may search for new teams in the NFL.

The trio has represented the upper echelon of football coaching for several decades. All three are in their early 70s, started their prolific careers on the defensive side of the ball, and spent many years working their ways up from assistants to coordinators to, finally, head coaches.

They presented as fiery competitors with serious demeanors on the sidelines, and they each found great success upon reaching the front of the bench. Belichick won eight Super Bowls — two at the helm of the New York Giants and another six in New England; Saban won seven national championships — one at LSU and six with the Crimson Tide; and Carroll won a Super Bowl in Seattle along with the two national championships he secured as head coach of the USC Trojans.

The new class of premier coaches — including the likes of Mike McDaniel of the Miami Dolphins, Kyle Shanahan of the San Francisco 49ers, and Sean McVay of the Los Angeles Rams — looks starkly different. They're all offensive-minded coaches and they're generally calm, cool, and casual on the sidelines. They're also very young, with an average age just over 40.

Belichick's split with the Patriots, Saban's departure from Tuscaloosa, and Carroll's ouster from the Seahawks mark more than just the end of an era; it's a changing of the guard that ushers in a new definition of what constitutes a great NFL coach.