In 2012, the Eagles' offensive line was so decimated by injuries that, by Week 9, they were down to only one of their original starters. In all, they used five starting lineups over the course of a season that, partly because of the O-line woes, ended with a 4-12 record.

This season, at least thus far, it’s been worse. The Eagles have lost two starters for the season, two other starters for an extended period, and starting right tackle Lane Johnson, who missed the opener and parts of two others games, is unlikely to be active Sunday when the Eagles host the Ravens.

“I miss Brandon Brooks, Isaac Seumalo, Jason Peters, Andre Dillard,” Eagles offensive line coach Jeff Stoutland said recently of the four injured starters. “Those are really good players, man. Those are good guys in the locker room, in the meeting room, and to have those guys not around is different to be honest with you.”

The last man standing has been center Jason Kelce.

In 2012, Peters was lost for the year during the offseason. Kelce suffered a season-ending knee injury in Week 2. Right guard Danny Watkins was done by Week 6. And right tackle Todd Herremans would follow suit two weeks later.

Left guard Evan Mathis would be the only starter to remain healthy all season. Then-offensive line coach Howard Mudd tried to juggle it all with a rookie, unproven youngsters, and veterans signed off the street. But it often looked like a car crash in slow motion.

One of the problems then might have been the Eagles' initial reliance on free agents to step in. Demetress Bell was a disaster at left tackle and had to be benched. And while Jake Scott eventually did fine at right guard, it took weeks to get him up to speed.

The other issue was that Mudd, despite being one of the best O-line coaches in NFL history, didn’t spend a great amount of time working with reserves at this stage of his career. So when King Dunlap, Dallas Reynolds, and Dennis Kelly were pressed into duty, they weren’t as ready as they should have been.

Jeff Stoutland, the Eagles' O-line coach since 2013, has had it maybe tougher this year because of the truncated offseason. But he has become one of the best developers of talent in the NFL and of molding youngsters into contributors often under tight deadlines.

The transition hasn’tbeen seamless for various reasons. Nate Herbig and Jack Driscoll were tossed into the fire in the opener, and quarterback Carson Wentz was pressured consistently. Jordan Mailata has had his ups and downs at left tackle. And Matt Pryor has struggled perhaps more than most of the replacements.

But the youngsters, under difficult circumstances, haven’t imploded, either. Many predicted they would collapse against the Steelers' vaunted pass rush last week. It wasn’t perfect, and they were assisted by chip blocks and max protection. But they seemingly did enough to win the game.

The Eagles didn’t win that game and haven’t won enough thus far. But one of the few positives of a disappointing season has been the early growth of the young O-linemen.

“I think they’re doing a tremendous job,” Wentz said Wednesday. “It’s always hard on the offensive line to have so many different moving pieces. There’s a lot involved, more than just X’s and O’s. You pass off games, and stunts and blitzes, and communications, a lot of things that people don’t realize that take time for guys to mesh together.”

Mailata might be the greatest revelation. There’s always been a kind of freak show interest in the left tackle because he was drafted as a novice and his immense size. But he has clearly shown that he can at least compete at this level.

But there are still reminders that Mailata (No. 68) started playing the game only just over two years ago, and that his start against the 49ers two weeks ago was his first at any level of football.

Pittsburgh linebacker Bud Dupree (No. 48) was a tough matchup, as he showed on that early power rush. But as the game wore on, Mailata wore him out. Still, Stoutland gave the 6-foot-8, 346-pound tackle a tough review after the game, warts and all.

“Just my hand work again, sticking guys, getting my hand timing right as well as being more physical in the run game,” Mailata said of Stoutland’s critique. “There’s a couple times where I was a little thrown off a block.”

But when Mailata is technically sound, there might not be an edge rusher who can get by him. Dupree tried to go wide here, but Mailata beat him to the spot with his vertical set, and it was as if the linebacker was up against a giant wall.

There has been speculation that Mailata will stay at left tackle even when Peters returns from a knee injury. If so, he could have a leg up on Dillard, the Eagles' 2019 top pick, next offseason.

“He still has a way to go, and he still has a lot to learn,” Stoutland said of Mailata."The one good thing is, he is a very unique individual. The guy can move his feet and change direction, and he’s so big. It’s hard to get around real big guys now."

Pryor (6-7, 332) is almost as big. While he shined in training camps the last three years, at least in one-on-one drills, the adjustment to live action has been more demanding. He failed to win the left tackle job when Peters initially demurred, and he couldn’t beat out Herbig for the right guard spot when Peters finally agreed to move.

But Seumalo’s knee injury forced Pryor into the lineup at right guard. He has survived, mostly with help from Kelce. But he’s had no choice but to learn on the job. The Eagles couldn’t get much going on the ground against the Steelers aside from Miles' Sanders' 74-yard touchdown run. Pryor (No. 69) and his block attempt on Stephon Tuitt (No. 91) here was a perfect example of why.

There were multiple players and reasons why the Eagles' running backs managed just nine yards on their 10 other rushes. But Pryor has often stood out for the wrong reasons.

“It’s not perfect or 100 percent on a grading sheet, but he’s done some really good things in there,” Eagles coach Doug Pederson said Wednesday. “He’s a big guy. He’s getting better each week.”

The Eagles brought veteran Jamon Brown in last month for depth, and he could be called upon if Pryor regresses. But the team has remained committed to their draft investments. And with Pryor, when his mental and technical approach match his physicality, it’s easy to see why. He pancaked Steelers linebacker T.J. Watt (No. 90) on this rush.

Herbig’s flexibility allowed Pryor to stay on the right where he’s more comfortable. For some linemen, balance becomes an issue when asked to switch sides.

“For Nate,” Stoutland, “it was not any issue at all.”

Herbig, of course, is also Kelce’s backup. He’s not as athletic as the other linemen, but he’s not a stiff either. His strengths start with his mind. He constantly asks questions of Stoutland and the other players and has used that Stanford degree to decode the various ways defenses will pass rush.

But Herbig (No. 67), at left guard, has natural power as well. Wentz’s pass here was batted at the line, but Herbig easily disposed of linebacker Vince Williams (No. 98) on this blitz.

Driscoll hasn’t played as much as the others, but aside from Week 1, he’s had the more difficult task of having to jump in mid-stream the last two weeks for Johnson, who has been in and out of the lineup with an ankle injury.

It’s looking as if Driscoll will start Sunday with Johnson in need of rest. The rookie exceeded expectations considering the short offseason and that he was drafted in the fourth round. He’s not especially explosive and will need to add more muscle next offseason, but he has yet to embarrass himself against some good edge rushers.

Watt is about as good as they come off the edge right now, and Driscoll (No. 63) was able to lock up the linebacker on this outside speed rush.

Driscoll committed a false start penalty in the game, and had some protection slip-ups as well. Handling stunts and twists can be the hardest adjustment for young guys.

“I don’t care if you’ve been playing next to someone for 10 years, the acceleration ... a tenth of a second makes a huge difference,” Stoutland said. “A call by a particular player telling the other guy, like ‘lickety-split.’ ”

Mailata and Herbig looked like a couple of old pros who have been playing alongside each other for 10 years on this Steelers play.

They benefited from a chip block, of course. Pederson made sure to give his tackles extra help from tight ends and running backs before they ran their routes. He also max protected on several of Wentz’s drops to varying degrees of success.

There are risks with keeping blockers to help with protection. On this late-game second down, Pittsburgh rushed just three, while the Eagles had only two receivers run vertical routes. Perhaps Wentz could have thrown to receiver John Hightower (No. 82, top of screen) as he completed his double move, but there was pressure, and he was sacked.

“You might have to give up something that way,” Pederson said, “in order to get something.”

The Eagles have already given up a lot in terms of injuries on their O-line. But they’ve gotten something in return: perhaps most significantly, experience for their future.