LOS ANGELES — What is the great cosmic sin that Philadelphia and its sports fans committed?

There must have been one.

How else to explain the black nimbi that seem to hover perpetually over the city’s professional teams? How else to account for what happened here at the Los Angeles Memorial Coliseum on Sunday?

The Eagles won a big game, beating the Rams, 43-35, to clinch the NFC East title and inch closer to a valuable first-round playoff bye. Yet everyone still had the feeling of frozen stones sitting in his or her stomach because of an unforgettable sight: Carson Wentz leaving the field, a towel draped over his head, a franchise’s entire fan base choking its breath.

For the record, it was exactly 7:05 p.m., Philadelphia time, when an Eagles spokesman began moving through the press box here and delivering the quick, brief diagnosis again and again like a hammer shot: “Wentz … knee … out.”

It was easy to pinpoint the sequence and moment that caused the injury and the subsequent dread: Wentz’s 2-yard touchdown scramble late in the third quarter, a play on which he took two hellacious hits from Rams defenders as he dived into the end zone, a touchdown that was erased because of a holding penalty by tackle Lane Johnson, a play that technically did not count … except in the worst of ways.

Four snaps later, on fourth-and-goal from the 3-yard line, Wentz was still in the game, and he somehow snaked a throw through a thicket of hands and helmets to Alshon Jeffery for a go-ahead touchdown. It was his 33rd touchdown pass, setting the team’s single-season record, and if that bitter and random alignment of excellence and anxiety doesn’t capture what it means to follow Philadelphia sports, nothing does.

In middle of stellar season: Wentz was in the midst of the finest season by an Eagles quarterback in the club’s 84-year history. He was the front-runner to be the NFL’s most valuable player. As he demonstrated again Sunday, his strength, intelligence, and athleticism allow him to escape tacklers, make throws, and generally play the position in a manner few other quarterbacks in the league can. He was the reason to think that, for the Eagles, a team that has never won a Super Bowl, everything might be different this season. And here we are, and everything feels as it always does.

After the game, Wentz left the Coliseum by riding on the back of a golf cart, his left knee encased in a large, black brace. The fear is that he tore the anterior cruciate ligament in the knee, and though head coach Doug Pederson did not confirm the nature of the injury, all anyone had to do to recognize its severity was stand outside the visiting locker room. One by one, the Eagles players and coaches filed out, each of them wearing a gray-and-green baseball cap commemorating the division championship they had just won, none of them smiling. None.

“It [stinks],” Johnson said. “There’s nothing you can really do about it. We came in wanting to win this game and clinch the division, and that part’s done, and I have the utmost confidence moving forward.”

Foles steps in at QB: I have the utmost confidence. It was the proper thing to say, the let’s-stay-positive thing to say, and in the aftermath of the wildest, most unpredictable victory of the Eagles’ season, it was understandable that Johnson said it. Nick Foles, himself once the prospective franchise quarterback, was solid after replacing Wentz, and a timely Chris Long forced fumble, two Jake Elliott field goals, and some inexplicably stupid penalties by the Rams were enough for the Eagles to escape.

In the locker room afterward, safety Rodney McLeod told Wentz, “We did that for you, man,” and maybe the Eagles did rally together and play better Sunday after losing their best and most important player. But the reality of what had happened and what it meant was settling in, too, and that sort of inspiration tends to have a short expiration date.

“I’m excited we won,” Foles said, “but I’m dealing emotionally with seeing him go down.”

No longer a title contender: The Eagles are 11-2, and next week, they could rout the hapless Giants and move to 12-2 even if emergency quarterback Trey Burton — who, while playing tight end, caught two touchdown passes from Wentz on Sunday — were to have to go under center.

But make no mistake: Without Wentz, it is asking too much to take them as a serious Super Bowl contender now. They were that, without question, with him. He was brilliant again Sunday — 23 completion in 41 pass attempts, 291 yards, four touchdowns — and all of it vanished like a wisp of smoke once he took those hits on that play that didn’t count but meant everything, once he started that long walk to the locker room, a walk from which he didn’t return.

All of it vanished, the hope for the sport’s greatest glory most of all.