And that puts them close to taking the next step to the playing field Sunday to play key roles in what looms as the Steelers' biggest game of the season.
Is the future looking any better for this defense?
"I'm not worried about the future," said Harrison. "I'm worried about Sunday."
On Sunday, the Steelers play at Cincinnati and hope to cut into the Bengals' 1 1/2-game division lead. But the Steelers will have to do it with their youngsters playing large roles on defense.
After Thursday's practice, defensive coordinator Dick LeBeau said that Jarvis Jones -- who's missed nine games with a dislocated wrist -- "is looking good" and might be activated from injured reserve.
"I think there's a good chance of that happening," LeBeau said.
Jones is in his second year as the primary blind-side pass-rusher, but last year's No. 1 pick has only three sacks in 17 games played.
"He improved steadily last year," LeBeau said. "You can go from the middle of the season on he was playing really good football. And he was playing pretty good football in camp. He's probably going to be a little rusty but he's a developing, good football player."
That's what LeBeau said about rookie second-round pick Stephon Tuitt, who'll make his first career start at left defensive end in place of Keisel. Tuitt has played bit roles in all 12 games this season and has made only six tackles.
"Everybody gets their opportunities and I'm sure he will make the most of this," LeBeau said. "He, again, is a developing young football player who has a solid future. There's nothing he's done that we've been unhappy with. And he's going to get more snaps, without a doubt. I think he'll do well."
He'll receive more snaps than Jones, who must still contend with Harrison, knee injury or not.
"It'll be a game-time decision," Harrison said, but only after Harrison had quickly answered "No" when asked if he would be giving way to Jones on Sunday.
Harrison said he felt pain in his knee following last Sunday's game and had an MRI, and "We are where we're at now," he said.
Harrison, of course, played for the Bengals last season and drew praise this week from Bengals coach Marvin Lewis.
"James looks great," Lewis said. "And after getting to know James last year, I’m not surprised one bit. He’s one incredible person and very strong-willed. When he puts his mind to something, he gets it done. I don’t know this for a fact but he looks like he’s slimmed down just a little bit on tape from what I can see. I have not spoken with James since he signed but he looks great. He’s making plays. He’s got an impact on the game."
And yet, Lewis cut Harrison last March. It allowed Harrison to retire a Steeler, come back, and now perhaps put a better finish to his career than the 30-tackle, two-sack season he had in Cincinnati. Harrison has 34 tackles and four sacks in nine games with the Steelers this season.
Is the Bengals game personal for him?
"No," Harrison said. "But it is an AFC North game, so it's big-time football."
It'll be big-time football with some youngsters who've never before been so involved.
The future is now, and the veterans the Steelers have left won't have any time to wet-nurse.
"Shoot, I better not have to," said Cameron Heyward. "We've just got to be ready to go. We've got to make sure these guys know what they're doing, and we've got to trust them, too."
Ben Roethlisberger practiced and his receivers commented that the zip on his passes was no different than it was prior to Roethlisberger smacking his wrist on a linebacker last Sunday. ... Troy Polamalu missed his second practice of the week with an illness, but he was at the facility joking with reporters. ... RT Marcus Gilbert missed his second practice with ankle and knee injuries and will likely be replaced again Sunday by Mike Adams.