ALAMEDA — It’s impossible to judge a draft class after one season, but the Raiders have the look of their second straight strong group of rookies.

Oakland’s top six picks from the 2015 draft have all started at least two games. Last year, the first six selections combined to make 63 starts.

“Great rookie class,” defensive end Khalil Mack, the team’s top pick in 2014, said of this season’s group. “Solid, solid guys on both sides of the ball. There’s been a lot of different impact players everywhere on the field, so it’s a great class.”

Amari Cooper, despite being slowed toward the end of the season by a foot injury, has lived up to his billing as the No. 4 pick by leading all rookies in catches (70) and receiving yards (1,050).

“It’s been a learning experience, getting accustomed to a new league and better players,” Cooper said. “It’s really encouraging. Guys are stepping up and making plays, being available. I’m just excited to see what the future holds.”

Cooper’s 14 starts headline the group, which also saw second-round pick Mario Edwards Jr. start 10 games before suffering a neck injury Dec. 20 against the Green Bay Packers.

Tight end Clive Walford, the third-round pick, has made two starts despite missing most of training camp with injuries and leads Raiders tight ends with 283 receiving yards and three touchdowns.

Fourth-round pick Jon Feliciano took over as the starting right guard two games ago and should go into next season expected to start at that position.

Both of the Raiders’ fifth-round picks — linebackers Ben Heeney and Neiron Ball — also are promising.

Heeney has started three of the last four games and notched 23 tackles and 1﻿1/2 sacks in that stretch. Ball picked up a couple of starts early and showed a knack for pass coverage before a knee sprain ended his season.

Coach Jack Del Rio considers his staff to be one whose strength comes in developing talent, be it rookies or undrafted free agents such as Seth Roberts, who has emerged this year after a season on the practice squad.

“We’ve created that kind of culture here,” Del Rio said. “I like that. Part of it is developing players. We feel like we’ve done a solid job in that category, and that’s not one that ends. We want to continue with that.”

The rookie class takes a lot of pride in the production it has delivered.

“I think we’ve just made a pretty big impact so far this year from pretty much everybody,” Heeney said. “We’ve got a bright future, and we’ve got a lot to build on for next year.”

For players such as Feliciano and Heeney who have worked themselves into the lineup late in the season, the experience is crucial.

“It’s definitely going to be beneficial for us to get our feet wet a little bit and just take that and roll with it into the offseason,” Heeney said.

Feliciano was the last of the group to earn a start, debuting against the Packers after an injury to Austin Howard forced a reshuffling of the offensive line. Watching his fellow rookies pushed Feliciano as he waited for his chance.

“I knew when my time came, I had to step up to what they’re doing,” Feliciano said.

Walford agrees: “Seeing your fellow rookie teammate doing well always motivates you to do better as well.”

It will be tough to top what the 2014 draft delivered, namely with a difference-making pass rusher in Mack and a franchise quarterback in Derek Carr. The draft also produced a steady right guard in Gabe Jackson, starting nose tackle Justin Ellis and versatile defensive back TJ Carrie.

General manager Reggie McKenzie’s first two drafts in Oakland didn’t produce as much as he’d like — running back Latavius Murray is the only starter remaining from the 2012 or 2013 drafts — but he’s making up for lost ground and building a group that’s producing and also making for a strong locker room.

“I think Mr. McKenzie and everybody upstairs does such a great job of bringing guys in through the draft,” Carr said. “Guys that can come in and contribute, guys that come in and are great locker room guys. That doesn’t happen all the time, but so far it’s been great.

“Everyone that comes in, you want to go hang out with those guys. That makes you want to go out, fight and battle with them, too. I think that they are only scratching the surface.”

Cooper (foot) participated fully in Friday’s walk-through and is listed as probable, as is safety Charles Woodson (shoulder) and Mack. Cornerbacks Neiko Thorpe (neck) and DJ Hayden (ankle) are questionable. Del Rio reiterated the hope that Cooper, who played just 22 snaps against San Diego, will benefit from the extra rest after Thursday’s game. “Getting to that Thursday is hard,” Del Rio said. “Playing the week after with 10 days is a good thing. We got through it OK.”