PHILADELPHIA — Back in June, Philadelphia Eagles tight end Zach Ertz said he had never been part of a team this talented, and that included the 2017 Super Bowl squad.

Coach Doug Pederson added in early September that this is the deepest roster he has had to work with since becoming the Eagles’ coach. The optimism heading into the 2019 season, both internally and around the Philadelphia region, was as high as it had been since 2004 when Terrell Owens was added to Andy Reid’s perennial contender.

Three weeks in, that optimism has been replaced with a pit in the stomach. The Eagles are 1-2, and now must turn around and play the undefeated Green Bay Packers at Lambeau Field on Thursday (8:20 p.m. ET, Fox). In a blink, they have moved too close to the cliff’s edge for comfort.

What happened? And are the Eagles in jeopardy of losing control of the season?

What are the main problems so far?

1. Injury and age. Receivers DeSean Jackson (abdominal strain) and Alshon Jeffery (quad) left early last week against the Atlanta Falcons and did not play versus the Detroit Lions on Sunday. The Eagles have lost two of their main defensive linemen, tackles Malik Jackson and Tim Jernigan, to foot injuries. Defensive tackle Fletcher Cox (foot), defensive end Derek Barnett (shoulder), safety Rodney McLeod (knee), linebacker Nigel Bradham (toe), cornerback Ronald Darby (ACL) and guard Brandon Brooks (Achilles) are among the players coming off surgery, and now Darby is dealing with a separate hamstring issue.

The Eagles shook up their medical staff for a second straight offseason after being slammed by injuries last season. This season is again off to a rocky start. One factor to consider is Philadelphia has the NFL’s third-oldest 53-man roster with an average age of 27.1 years. Eight of the Eagles’ original starters are 30-plus, and four more are 29 years old.

“If you’re going to draw a parallel, I guess maybe that’s what people would think: older roster, injuries,” coach Doug Pederson said. “But even some of the injuries are probably an effect of, it’s football. It’s a rough sport and it’s hard to put a finger on some of them. … I will say this: Guys have battled through injury to play, they continue to do that, and that’s a positive thing.”

With so many guys banged up, expected production hasn’t been realized in key areas, including …

2. Pass rush. Getting after the quarterback with an organic four-man pass rush is defensive coordinator Jim Schwartz’s bread and butter, but the defensive front has been largely ineffective in this respect through three games. The Eagles are second to last in the NFL with two sacks. The lone lineman to register a takedown is Jernigan, and he now has a broken foot. The lack of an organic rush has forced Schwartz to dial up more blitzes — and in particular, more all-out blitzes — than he prefers. That’s left the back end vulnerable. Four of the opponent’s seven passing TDs have come when the Eagles sent five or more after the quarterback. The mix of shaky cornerback play and an anemic pass rush has led to some big plays for the opposition.

Also, Cox has not looked like himself yet this season. The main cog to what the Eagles do defensively, they need him to round into form, and soon.

How much of this falls on Carson Wentz?

Not a ton. He has been working without his top two receivers for most of the past two games, and has not gotten much help from their replacements. Eagles’ skill position players had seven drops on Sunday alone. Last week, Nelson Agholor couldn’t hold onto a pass late, and it cost the Eagles a chance to win the Falcons game. Same for JJ Arcega-Whiteside against Detroit. Take away a couple of the offensive miscues, and the Eagles are 3-0 and this story isn’t being written.

Wentz can improve, especially early in games, but he’s not the problem. He’s one of the really good players on this team who is helping to keep things afloat.

Are the Eagles in serious trouble?

Serious trouble might be a touch strong given how early in the season it is, but there is reason for concern. DeSean Jackson’s injury is key. One doctor recommended surgery to fix his abdominal injury, a source said, but he’s opting to play through it and is expected to return after Thursday’s game in Green Bay. The idea that he will be at 100 percent at that time seems like a stretch. If he is limited, or ends up sidelined long-term, the offense will be without the explosive element central to the operation.

That would only heighten the importance of younger players such as rookies Miles Sanders and Arcega-Whiteside and second-year tight end Dallas Goedert (calf) to mature quickly, and for some of the veterans such as Cox and members of the offensive line to look like more youthful versions of themselves.

The schedule has little give to it from this point forward. Thursday’s game is the start of three of four on the road, followed by home games against the Chicago Bears, New England Patriots and Seattle Seahawks.

If there is in fact championship mettle inside this team, it’s time to show it.