The reigning NFC champions were flat Sunday and Eagles head coach Nick Sirianni had a theory why: he didn’t play his best players in the preseason. Quarterback Jalen Hurts, receivers A.J. Brown and DeVonta Smith and blockers Jason Kelce and Lane Johnson were among the offensive players who didn’t take the field for a single exhibition snap this year.

“If I had to do it over again right now,” Sirianni said Sunday, “I would say, ‘Yeah, I would have played starters one or two drives in the preseason.’”

Sirianni said that after a Week 1 win — on the road, no less, against the Patriots. His offense sputtered, though: Hurts finished with a 89.2 passer rating and 170 passing yards.

If Sirianni can show such self-reflection, why can’t Matt Eberflus? Despite his claims otherwise, the Bears weren’t ready to play in Sunday’s 38-20 season-opening loss to the rival Packers at Soldier Field. The disaster, which unfolded in front of God and Dick Butkus and everyone else, was the Bears’ fourth-worst season-opening defeat since the 1970 NFL-AFL merger.

Still, Eberflus — whose Bears have now lost 11-straight games over the last two seasons — swore his team was prepared. He pointed to a first half in which the Bears were merely outscored by four, an odd thing to be proud of.

“I thought it was solid football up to that point,” Eberflus said Monday. “I thought the defense made some good plays. I thought the offense made some good plays. To answer your question, I would say yes, they were ready.”

If that’s the look of a team that’s ready to play, the Bears could end up being the worst team in the NFL again this year.

Eberflus better hope quarterback Justin Fields was merely rusty, even if that turns out to be a problem of the coach’s own creation. Eberflus played Fields in only 20 of the Bears’ 181 preseason snaps — about 11% of their plays. The Bears sat him for their second preseason game, content with the work he got in two joint practices against the Colts.

Sunday, Fields pushed back on the notion that he was unprepared for Week 1 because he didn’t play much in the previous month.

“That has no correlation,” Fields said.

The Packers’ Jordan Love played 57 of his team’s 196 snaps — or 29%. His 123.2 passer rating Sunday was the best in the NFL entering Monday night’s game.

Coincidence?

“You’ve gotta find a formula that works for you,” Eberflus said. “Each individual team’s different, because you’ve got experience and you’ve got youth on all different teams. And it’s all varied by the positions.”

Cornerback Jaylon Johnson said preseason inaction wasn’t a “big deal” for the defense, which didn’t commit a penalty on that side of the ball and only totaled nine missed tackles. Rusty teams typically have more.

Eberflus was intentional in the amount of work he gave his players this preseason, consulting with his medical staff and crafting three different speeds of practice — red, yellow and green, like a stoplight — that dictated snap counts.

The Bears were struck by injuries nonetheless —center Lucas Patrick, guard Nate Davis and receiver Chase Claypool, all offensive starters Sunday, didn’t play a single preseason game. Guard Teven Jenkins did — but landed on injured reserve and won’t play until Week 4 at the earliest.

Eberflus said that he’s noticed in recent years that, around the league, some offenses start slow because of the lack of preseason work. He bemoaned the lack of two-a-days during training camp — where coaches, he said, can “out a little grind on ‘em” — to get teams ready.

Those aren’t ever coming back. Eberflus has to adjust.

When Eberflus chose to sit his healthy players this preseason, he sent a message that they were ready to go. The Packers proved that they were anything but.