Redskins quarterback Kirk Cousins threw a crucial interception and lost two fumbles in Sunday’s loss. (Toni L. Sandys/The Washington Post)

After the slow-starting, misfiring Washington Redskins bumbled through the preseason, fans’ best hope was that Coach Jay Gruden was saving his most dynamic play-calls for the regular season. Or, perhaps, that players were holding back in the interest of personal safety to ensure they’d be healthy enough to unleash their true ability on opening day.

Any hope that the Redskins would magically flip a competitive switch when the games mattered — starting with Sunday’s regular season opener at FedEx Field against the Philadelphia Eagles — proved misplaced, as the Redskins fell behind by two scores early and never recovered, suffering a 30-17 defeat to their NFC East rival before a crowd of 78,685.

The Redskins have lost five consecutive season openers — and their fourth under Gruden. And they had their five-game winning against the Eagles snapped, thanks in large part to the efforts of second-year quarterback Carson Wentz, who completed 26 of 39 passes for 307 yards, two touchdowns and an interception.

For Redskins quarterback Kirk Cousins, playing for a second consecutive season on the NFL’s one-year franchise tag, it was a rocky and bruising afternoon. He accounted for three of the Redskins’ four turnovers — including a goal-line interception — and was sacked four times, with right tackle Morgan Moses twice allowing Eagles defenders to topple him. While Cousins ran successfully for three first downs, trying to achieve with his legs what he couldn’t through the air with a largely remade receiving corps, he took a pounding in the process. His final stats: 23 of 40 for 240 yards, one touchdown, one interception and two fumbles.

All told, the sketchy performance smacked of a team that’s not ready for the regular season and lacks the tools, or perhaps the will, to fix shortcomings that have been evident since its humiliating loss at Baltimore to open the preseason.

Gruden, however, said much of the offense’s struggles were due to the Eagles’ swarming defense.

“You attribute sloppy offensive play to good defensive play,” Gruden said afterward.

Washington’s revamped defense, a unit that features seven new starters and boasted much of the offseason of its new, attacking mind-set, kept the game in reach despite the turnovers. But it, too, got off to a slow start, allowing Wentz to escape the grasp of two defenders and throw off-balance for a 58-yard touchdown on the Eagles’ opening possession.

“When you put yourself in a hole it just makes it that much harder,” said outside linebacker Ryan Kerrigan, whose second-quarter interception return of 24 yards accounted for the Redskins’ first points, paring the Eagles’ lead to 13-7 following the extra point. Teammate Stacy McGee tipped the pass.

Kerrigan later combined with Matt Ioannidis for a drive-ending sack.

But the 6-foot-5, 237-pound Wentz endured, looking at moments like a young Ben Roethlisberger who may well pose a problem for the Redskins for years to come.

As was true in the preseason, the Redskins’ running game lurched in fits and starts, accounting for just 64 of the Redskins’ total 264 offensive yards. Running back Rob Kelley averaged three yards on his 10 carries; Cousins added 30 more rushing yards.

The passing game clearly misses Pierre Garcon and DeSean Jackson, its most productive and explosive wide receivers from last season, who left for higher-paying jobs in the offseason in San Francisco and Tampa Bay, respectively.

In their stead, the 6-4 Terrelle Pryor Sr. is proving a less reliable target. He caught just six of the 11 balls thrown his way Sunday. Two potential touchdowns went wanting as Cousins-to-Pryor deep throws fell incomplete. And Josh Doctson, the first-round draft pick from 2016, was a mere footnote — rarely on the field, never targeted and a ghost on the stat sheet, relegated to backing up Ryan Grant.

None of this is friendly to Cousins, who set back-to-back, single-season franchise passing records the past two years. But Cousins did nothing Sunday to shake his reputation for grievously timed turnovers. He marched the offense to the Eagles’ 14 early in the fourth quarter, the Redskins trailing 19-17, only to throw high enough over Jamison Crowder’s head that Eagles cornerback Jalen Mills had an easy interception on the goal line.

“You’ve got to be able to make that play there,” Cousins said afterward. “If we do, we get the first down. It’s a different ballgame. Those are the plays you look at and say, ‘Got to be better.’ ”

Cousins then compounded matters — dashing any hope of a late comeback — with a fumble inside the two-minute warning that sealed the outcome. Defenders converged as Cousins dropped back to pass, the ball squirted out and Philadelphia’s Fletcher Cox ran it in for a touchdown.

The two-point conversion succeeded (on a Wentz completion to Alshon Jeffery), making it 30-17 with 1:29 remaining.

There were bright spots, but they were few.

Among Redskins pass catchers, the 5-8 Chris Thompson proved toughest. With less than two minutes remaining in the first half, Thompson caught a ball over the middle, took a pounding from an Eagles defender and motored for a 29-yard touchdown reception that gave the Redskins their only lead, 14-13.

“That’s my job,” said Thompson. “I got to make plays with the amount of snaps I get.”

But the lead was short-lived.

In the end, Sunday’s high-stakes season opener changed nothing about the Redskins team that struggled through the preseason. The Redskins now head into Week 2 sputtering on offense, mistake-prone and simply not ready for games that count.