The Nick Sirianni era came crashing back to earth after a deflating 17-11 loss to the 49ers on Sunday. The losses were sure to come, but the Eagles let one slip away, and did so in untidy fashion. Win, lose, or draw, here’s what we learned:

Nick Sirianni is going to have first-year coach moments. In last week’s opener, Sirianni had his players prepared. He devised a game plan that allowed his quarterback and offense to play to their strengths. He made smart in-game decisions. And he was thus rewarded with his first NFL victory. But Sirianni had weeks, months, and, well, years to plan for that moment. What would he do with just a week to prepare against stiffer competition?

He got off to a solid start. The Eagles did drive past the 49ers’ 30-yard line on three of their first four possessions. He did have two solid third-down calls — a Miles Sanders option run and a mesh-concept pass that beat man coverage — early on. But a dubious set of plays when the offense faced first-and-goal at the 1-yard line ultimately was Sirianni’s undoing.

You could argue that he got too cute down there. Why not just sneak Jalen Hurts four straight plays from that distance? “I think that that sneak is a little bit more from a little closer, to be honest with you,” Sirianni said. San Francisco does have one of the best defensive lines, and the Eagles had just replaced the injured Brandon Brooks with rookie Landon Dickerson. But the issue wasn’t as much the calls as it was design.

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On first down, Sirianni had Hurts roll to his right off play-action. Zach Ertz was his first read, but he was covered and there wasn’t another option to that side. On second down, Sanders was dropped in the backfield after he had to leap Isaac Seumalo, who was cut by a 49ers defensive tackle. Did the officials miss a penalty? Perhaps. The Eagles were now 4 yards out, and on third down, there was a run-pass option with Ertz the latter on a potential shovel pass. Hurts didn’t like the look for whatever reason, but the run wasn’t there either. And there didn’t appear to be another throwing option as Hurts rode Sanders to his right.

I’ve heard the fourth-down call — Sirianni’s version of “Philly Special” — described as pandering. Maybe. But to me, the bigger problem was more the design. Greg Ward’s only throwing option — as far as I could tell — was Hurts. Where was the safety valve? If Nick Foles was covered in the Super Bowl, Trey Burton still had an open Torrey Smith. The Eagles still had more than a half of football left, but that failed sequence haunted Sirianni.

Some wanted him to take the three points for a 6-0 lead there, but analytics supported his aggressive decision. You could argue he was too conservative on his first two fourth-down choices, though. He opted for Jake Elliott to attempt 45- and 47-yard field goals rather than go for it on two fourth-and-3 decisions. The second attempt was blocked.

Hurts is still a work in progress. My column off the game was about Hurts, but I had a few more thoughts that didn’t make print. Sirianni seemed to be compensating for Hurts’ NFL-low air yards (3.7) in Week 1 with a number of shot plays. The 49ers were banged up in the secondary, so you can understand the coach testing their back end. But Hurts completed just 1 of 4 deep balls and finished with a league-high 14.6 air yards without the desired results. I guess you could say that showed trust in the quarterback, but the Eagles were essentially without an intermediate passing attack.

Hurts can throw from the pocket. He can look off his first few reads and complete passes. It may not be a strength yet, but Sirianni has to give him opportunities. Yes, you want to win games, but Hurts will not develop if he’s asked to only execute RPOs and one-read shot plays. He has two more-than-competent tight ends. It shouldn’t have taken more than three quarters for Ertz and Dallas Goedert to be targeted. Sirianni went heavy with three-receiver sets (75%), up from 60% in Week 1. The Eagles will need to be explosive, but DeVonta Smith, Quez Watkins, and Jalen Reagor are still young and growing. Use them and push them, but not at the expense of your best talent. A tight end, as they say, can be a young quarterback’s best friend, particularly from the pocket.

» READ MORE: Eagles defense held up against 49ers, but a few costly penalties ‘sucked the air out of’ them

The Eagles are going to have sloppy moments. Lost in the Eagles’ Week 1 win were their 14 penalties, and understandably so. But Sirianni knew he had to clean up the mistakes. The Eagles didn’t draw as many flags on Sunday, but eight is still too many, especially when a few were personal fouls. The most egregious came in the fourth quarter after a 49ers fumble out of bounds. The Eagles would have forced a long third-down situation, but Derek Barnett needlessly bulled over a 49er and gifted a first down. It was the eighth personal foul of his career. Barnett’s play hasn’t earned him the benefit of being a repeat offender.

He wasn’t the only Eagles player to have erred Sunday. Arryn Siposs dropped a beauty of a punt inside the 5-yard line and Andre Chachere kept it from going into the end zone, but Zech McPhearson needlessly touched the ball and it resulted in a touchback. And then there was the blown coverage that allowed the 49ers their first touchdown. Cornerback Steven Nelson appeared to be the guilty party when he left his assignment — receiver Jauan Jennings — to cover an already-covered George Kittle. “A lot of things got jumbled up,” Nelson said. That was the 12th and final play of a 97-yard drive.

Defensive coordinator Jonathan Gannon has seemingly decided that he will risk long drives at the expense of big plays. He has leaned heavily on zone coverage with a fair amount of Cover 2. And, for the most part, it has been effective. But you have to deliver in the red zone and the Eagles didn’t fare as well as they did last week inside the 20. Still, it’s difficult to find great fault with Gannon’s defense. The 49ers scored only 17 points and averaged only 4.5 yards per play. That should be enough.

The Eagles’ depth will be tested after key injuries. Brandon Graham is likely done for the season with a ruptured Achilles tendon. Brandon Brooks is believed to have torn a pectoral muscle, which could also end his season. Graham has been a mainstay for years, and while Brooks can’t seem to avoid injury, he has been an anchor in the middle of the offensive line. Injuries are reasons why Howie Roseman continues to invest in the big guys up front. It’s time for their replacements to deliver.

It will be a group effort on the defensive line, but Josh Sweat and Barnett will shoulder the load. Sweat, somewhat surprisingly, played only 40% of the snaps (28 of 70) Sunday. We’ll find out the Eagles’ explanation later. But didn’t he just sign a three-year, $40 million contract? Is he being saved? Can he play starters’ snaps? Defensive tackles Fletcher Cox and Javon Hargrave led the unit with 51 and 50 snaps, respectively, but it’s fair to wonder if they wore down by the fourth quarter. The 49ers adjusted to the interior line’s effectiveness with a toss run play to the outside that negated their push.

Hargrave was again the Eagles’ best D-lineman. Cox has been disruptive at times, but he also has been relatively quiet in the first two games. The unit as a whole didn’t apply much pressure to 49ers quarterback Jimmy Garoppolo. He got the ball out quickly, but he was hit only twice and never sacked. Gannon isn’t going away from his early-down usage of a 3-4 front. But it does put some ends in four-/five-technique spots they’re not normally accustomed to. Is Ryan Kerrigan best suited to the interior?

I was surprised when rookie Tarron Jackson made the 53-man roster, but he was on the field for 11 snaps after Graham left. That meant he had to slide inside in 3-4 looks and he got bottled up. On the other side of the ball, Dickerson got the nod when Brooks left. Nate Herbig might have been the better immediate choice, but you don’t expend a second-round draft pick to have him sit. Dickerson had only one full practice of preparation, so you could excuse some of his lesser moments. He should improve with time, but there will be a learning curve.

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Extra points. As for the injuries, there may be some public grumbling about the lack of training camp and preseason playing time, or the Eagles’ medical and sports science staffs, but Graham’s and Brooks’ injuries likely had nothing to do with conditioning. It’s more about their advanced age. Older players get hurt at a higher rate. It’s just that simple. … It sure looked like the low trajectory on Elliott’s 47-yard field-goal attempt was the cause of the block. “I felt like he had to drive it from where we were on the field,” Sirianni said. It’s not like the 49ers’ Javon Kinlaw got his hand on the ball. It hit him in the forearm. … Nelson had what could have been the Eagles’ first turnover of the season when Garoppolo threw late on a third-down out route. He couldn’t hang on, though. Not only have the Eagles yet to take the ball away, they’ve yet to give it away. … The atmosphere at Lincoln Financial Field to open the game was electric. It had been nearly two years since full attendance was allowed and you could sense how appreciative fans were to be back. The stadium was near-full by the national anthem. The last time I can recall that being the case was the NFC championship game in 2017.