ATHENS – Kirby Smart stood on the field at Sanford Stadium early last October, alone and talking to no one for a moment. His head was turned to the left, where the Georgia football team was warming up for its game against Alabama.

And Smart’s lips were curved up, into a calm, contented smile.

It was a snapshot, one this reporter filed away for further use, and given all that’s transpired since then, one of the lingering moments of the season.

The Alabama defense that Smart takes into Monday’s national championship game will have two things that the Georgia defense he takes over on Tuesday has not had: Depth and experience. And that speaks to the way Smart helped build things in Tuscaloosa, and how Georgia was doing things the past few years – but too late.

“There’s not a whole lot of experience, okay?” said Jeremy Pruitt, then Georgia’s defensive coordinator, and now set to be Smart’s replacement.

The truth is that Pruitt and his defensive staff did a very good job this season to get Georgia ranked eighth nationally in defense. That’s one of the reasons why two of them (Kevin Sherrer and Tracy Rocker) have been retained by Smart, and the other two (Pruitt and Mike Ekeler) have moved on to be defensive coordinators. (Ekeler is set to be hired at North Texas.)

But Alabama has the nation’s second-ranked defense – the seventh time in eight years that it has had one of the nation’s top five ranked defenses, and four times it’s been No. 1. Georgia has been in the top 5 just once in that span, in 2012, and that was No. 5.

Jeremy Pruitt reinvigorated Georgia’s defensive recruiting. (SONNY KENNEDY/SPECIAL)/Dawgnation)

The main reason is simple: Alabama has been building its defense through great and stable recruiting.

Georgia, until Pruitt’s arrival, had not.

The Bulldogs’ signing class in 2013 – the last of the Todd Grantham era – serves as a poster child that bigger is not better. It included 34 players, but only 17 were still with the team at the bowl game last week. Several of the highest-rated defensive players (Tray Matthews, Shaq Wiggins, Brendan Langley) transferred or were dismissed.

Then there was the 2012 class, where three of the four highest-rated defensive signees were either dismissed (Josh Harvey-Clemons and Jonathan Taylor) or transferred (Sheldon Dawson). The exception, outside linebacker Jordan Jenkins, did pan out.

The transition-marred 2014 class, which came after Pruitt took over less than a month before signing day, has at least reaped Lorenzo Carter, Malkom Parrish and the surprising three-star Dominick Sanders. But three other defensive signees are already gone, and another (Lamont Gaillard) was moved to offense.

Pruitt and Georgia finally felt they got it right with the 2015 class, with eight players who started at least one game this season. Trent Thompson, Roquan Smith, Natrez Patrick and Rico McGraw could be stars at Georgia someday, as could several others.

But if they are, it will be for Smart.

Alabama, meanwhile, has consistently recruited at an elite level, on both sides of the ball. The starting lineup includes six seniors and three juniors. The Crimson Tide have had far fewer of the high-profile flameouts. In fact the biggest one was someone who came from Georgia: Taylor.

This week, as Smart was talking about the defense he takes to the national championship,

“We’ve never had one this deep,” Smart said. “This group is pretty deep. They can roll in and out (of the game) and not drop off a lot.”

That’s what Smart hopes to build at Georgia. Pruitt and his staff started laying the foundation. If Smart can keep it going, Georgia’s defense can be consistently good, perhaps as dominant.

The offense? Well, that may be the biggest undertaking. But Smart can at least look at the defense he inherits in Athens, and know he has reason to smile.