ALAMEDA — The Raiders defense experienced a youth moment throughout this season, which concludes Sunday in Kansas City.

Some of that was by necessity after Justin Tuck’s season-ending pectoral injury and Aldon Smith’s yearlong suspension. Some has been performance-based, such as Curtis Lofton ceding most of his inside linebacker snaps recently to rookie Ben Heeney.

It’s added up to a defense that appeared to be the Raiders’ weakness early in the year becoming its strength over the season’s final month.

“I think it’s huge for us as an organization to understand that there are a lot of ways to win a game,” Del Rio said. “We talk about complementary football and you’d like to be crisp in all three, but the bottom line is as long as you keep fighting, you have a chance. You can keep yourself in games. I feel like we’ve done some of that with our defense here over the last month or month and a half where defensively, we’ve been in games.”

That’s in stark contrast to early in the season when, as Del Rio put it, “our offense was red hot and was carrying it and the defense was having its struggles.”

At the midway point in the year, the Raiders were 30th in yards allowed (411.5 per game) and last in passing defense, allowing an average of 314.6 yards per game that stood in line to be the worst in franchise history.

Oakland approaches the finale Sunday in Kansas City ranked No. 22 in total defense, allowing 365.3 yards per game.

“I think putting in a new defense and playing with a new group of guys — a lot of guys, this is their first year playing together — it takes some time to develop a chemistry,” defensive tackle Dan Williams said.

The turning point seems like a strange one. Smith was suspended after the ninth game, with the Raiders still ranked 30th in total defense, and they’ve allowed just 300.3 yards in the six games since.

The absences of Tuck and Smith first opened the door for rookie Mario Edwards Jr. With him missing the final two games of the season with a neck injury, two former undrafted free agents Denico Autry and Benson Mayowa have emerged even more.

“There’s a reason why they’re here, they can play,” Williams said of Autry and Mayowa. “It just goes to show the way our guys here can evaluate talent and those guys are going and showing it out on the field.”

The Raiders have held three of their past five opponents under 300 yards. That hasn’t necessarily correlated into wins — Oakland is 1-2 in these five games allowing under 300 and 2-0 giving up more than 300.

That’s because the scoreboard has been deceiving in terms of the defensive effort. The Chiefs and Green Bay Packers put up 34 and 30 points, respectively, despite low yardage outputs. Both teams returned Derek Carr interceptions for a touchdown, while Kansas City had two other short touchdowns drive off Carr picks and the Packers had one more.

But it’s easy to argue the defense has given the Raiders a fair chance to win each of the past six games and has done so behind a young group. Williams, at 28, is the oldest player who figures to return in a prominent role next year.

Retiring safety Charles Woodson, 39, and Lofton, 29, are the only players older than 26 who have played more than half of the defensive snaps and Lofton is coming off a game when he was relegated to a season-low eight defensive plays.

The core of that group obviously starts with second-year star defensive end Khalil Mack, who will turn 25 in February. Edwards won’t turn 22 until January.

Autry is 25, Mayowa is 24 and linebackers Heeney and Neiron Ball, who had a nice stretch earlier this year before a season-ending knee injury, are both 23. Malcolm Smith, 26, qualifies as the veteran of the linebacker group.

“It’s very encouraging,” Mack said of the young group. “You’ve got a lot of different guys. We’ve just got to focus in on what we need to do in the offseason, but at the same time, our focus is to get this win this weekend.”

The secondary needs to most help with Woodson’s departure, but waiver wire pickup David Amerson is 24 and has been terrific and Woodson gave his stamp of approval for this defense’s future.

“I think they are starting to figure it out,” Woodson said. “The team is really starting to jell together. … Things didn’t work out quite the way we wanted them to, but we kept fighting and we’re going to continue to fight throughout this last game.

“But it’s a good, young, group, now. A bunch of young guys that this team is going to be able to grow with for the foreseeable future and it’s going to be exciting to watch them going forward.”

Mack (knee), wide receiver Amari Cooper (foot) and cornerback Neiko Thorpe (neck) remained limited in practice Thursday.

Cornerback DJ Hayden sat out practice with an ankle injury, apparently suffered during Wednesday’s practice.