SANTA CLARA, Calif. -- On the same field that hosted Super Bowl 50, one of the greatest games in Denver Broncos history, the team collapsed on itself Sunday, like a dying star.

For three weeks the Broncos had fought, scraped and clawed their way back to .500 and had put themselves on the fringe of the AFC's playoff race. And then, despite another scramble to the finish, they made quite the football mess at Levi's Stadium in a 20-14 loss to the San Francisco 49ers.

"We didn't play well in the first half, obviously, defensively we gave [George] Kittle way too many opportunities ... and that's unacceptable, and offensively we had about 69 yards in the first seven drives; we did not play well in the first half at all," said Broncos coach Vance Joseph. " ... In the second half ... we tried, the guys played hard ... simply we didn't play well, no excuses."

How bad was it? Start with Kittle, the 49ers tight end, being mentioned in the same sentence as Hall of Famer Jerry Rice in the single-game portion of the 49ers record book. Toss in more than a few penalties, including five defensive penalties on one San Francisco scoring drive alone. Add an offense that spent much of the day spinning its wheels, and finish it off with a general lack of desperation for a team that said it had plenty.

Put it all together and the Broncos got what they deserved. This loss is on them, and if this doesn't prove just how valuable a player cornerback Chris Harris Jr. is, then you're just not looking.

"We got outplayed," said Broncos defensive end Derek Wolfe. "They just outplayed us."

The Broncos had opened the day with a sliver of a playoff chance and the old take-care-of-their-own-business opportunity, but they didn't take care of their business. Nowhere did it show up more than in how the Broncos handled Kittle, who came into the game with 33 more receptions and 576 more receiving yards than the next 49ers player.

It sounds and looks like the Broncos had only one job, and yet the Broncos couldn't reel in Kittle until the second half, when the 49ers went into run mode to grind the clock. With Harris out after he suffered a fractured fibula against the Bengals, the Broncos have limited options, but there were times in the first half it looked like they were running things on defense they hadn't practiced.

As a result, Kittle had 94 yards receiving at the end of the first quarter, 210 yards receiving at halftime -- the most receiving yards any Broncos defense had surrendered to any tight end in any full game. He did it against a defense trying to cover up the fact its best player in coverage -- Harris -- is recovering from a fractured fibula.

"People don't have to talk about [Kittle] for us to know he's good, he's a thousand-yard receiver at tight end," said Broncos safety Su'a Cravens. " ... It's not frustrating, we're all professionals, he's going to make his plays, and we've got to make our plays. We just beat ourselves, plays we normally make, we weren't making them."

That all of this was orchestrated by Kyle Shanahan, the son of a two-time Super Bowl winner for the Broncos, added just a little more salt in what had the feel of a season-ending wound. Shanahan, of course, didn't get the Broncos job because Vance Joseph did, and Shanahan had turned some heads this week when he offered he never really thought the Broncos were going to give him the job.

The loss was not without reason. Wide receiver Emmanuel Sanders ruptured his left Achilles tendon this week, making him the sixth starter on offense to go on injured reserve this season. The Broncos often lined up three receivers who were rookies this year or spent their rookie year in 2017 on the Broncos' practice squad.

They have three reserves on the offensive line, essentially playing four tackles in the lineup with their former starting guard, Connor McGovern, at center. In the end, Sanders' injury, coupled with Harris' injury, over the course of a 72-hour span this past week, proved to be the last straws.

The Broncos had shown the ability to overcome plenty here and there, but Sunday they just looked tired, really tired, and couldn't overcome themselves.

It puts Joseph back under the microscope.

Because while the Broncos were still out there swinging for Joseph on Sunday, they still went down, and went down hard.

"We're in the NFL, we get paid to do this, the next man up has to step up, and we didn't step up," said running back Phillip Lindsay, who finished with 30 yards rushing. "... We didn't execute the plays that were called, and that's on us."