What in the world happened with covering George Kittle?

Entering Sunday, George Kittle was the San Francisco 49ers’ offense.

There were no ifs, ands or butts about it.

And it was no surprise to anyone — including, and seemingly most importantly, the Denver Broncos.

“We clearly saw what they were doing on film and we knew that was a player that we had to take out of the game,” safety Darian Stewart stated after the game.

After 30 minutes of play, and up 20-0, the 49ers’ offense, aka No. 85 Kittle, had no problem moving at will against Denver’s defense.

The first thing head coach Vance Joseph pointed to about the porous first half play on both sides of the ball was the way Kittle sliced and diced his team’s defense.

“He’s a great player. We knew coming in he was going to be the guy we had to get stopped and we didn’t get it done,” a disappointed Joseph said after his team’s 20-14 loss.

“We didn’t play well in the first half. Obviously, we gave Kittle way too many opportunities.”

Out of the gate, the offensive mastermind Kyle Shanahan was as predictable as could be, having his inexperienced quarterback Nick Mullens target Kittle — a quarterback’s best friend — early and often.

At the end of the first quarter, the then 2-10 49ers had an early 3-0 lead. More damning, however, was the 6-foot-4, 240-pound tight end had four catches for a whopping 94 yards. In just one quarter of play.

But that was just the start.

After Denver’s third-straight punt to start the game, San Francisco, unsurprisingly, went straight to the heart, soul, body and mind of their offense.

Mullens found a wide-open tight end named Kittle in the middle of the field begging for the ball once again.

After the easy catch in stride, it was off to the races. Fittingly, it was 85 yards to the house for No. 85.

“Blown coverage,” Joseph simply said, describing what possibly happened.

“He took some 10-yard plays the distance today,” Von Miller said, dumbfounded. “There’s not too many tight ends in the league that can do that.”

Kittle’s line inexplicably read: Five catches for 179 yards and a dancing trip into the end zone. This, of course, was with 9:47 left in the second quarter.

At this point, Kittle was already in the record books, recording the most receiving yards ever by a tight end in a single game against Denver’s defense.

Additionally, in less than 30 minutes of play, Kittle had more receiving yards than Denver’s starting tight end, Matt LaCosse, had all season.

On his very next catch, Kittle notched another record. After his 13-yard reception two drives later, Kittle’s 192 receiving yards became the most ever in a single game by a 49ers tight end.

“We had one blown coverage and a couple where we just didn’t cover him and he beat us one-on-one,” Joseph said, attempting to explain what happened to allow Kittle to run free.

After all of this, the bleeding still wasn’t over as the Iowa product noticed one more reception for an additional 18 yards to top 200 receiving yards in the first half.

“He was open every play, man. It was crazy,” Mullens said brutally honest after the game talking about this star tight end. “Shoot, all the receivers were.”

His halftime stats showed it.

His halftime line was something out of a video game: Seven catches on eight targets for 210 yards and a touchdown.

“Unacceptable,” Joseph stated about the enormous numbers in the first half.

Once again, Kittle was in the record books for all of the wrong reasons in Denver’s perspective.

His 210 yards at the break marked the most receiving yards by any player at any position since 1991 — two years before the unguardable Kittle was born.

Not only that, but the league’s second-leading receiving tight end came four yards short of breaking the single-game receiving record for yards by a tight end. That record (214 receiving yards) was set by Denver’s own Shannon Sharpe in 2002 and he needed an entire game to do so.

George Kittle needed one half to get within four yards of the all-time record.

“He probably had 100-something yards on busted plays alone, so that doesn’t help,” safety Justin Simmons said, trying to explain what went completely awry.

“He’s a great player, so he’s going to get his catches. He just played a great game today. He’s a great player. I consider him one of the top tight ends — one of those guys like [Travis] Kelce and Delanie Walker. He’s the real deal. One-thousand yards for a tight end. We did a good job stopping him in the second half, but first half we kind of beat ourselves. With a player like that, you can’t do that.”

In the first half, he was on pace for 420 receiving yards and the 49ers — with a third-string quarterback and a fourth-string running back — were on pace for 40 points.

Thanks to the Kittle monster.

“Eighty-five is a hell of a player. George Kittle is a hell of a player,” Von said without a doubt. “We knew coming into the game that he was going to be talented and that he was going to make plays, but the plays that he made today, he just killed us. On top of the penalties, and on top of my penalties in crucial situations. It just killed us.”

After a much-needed halftime break, the bleeding stopped.

But it was too little too late.

In the third quarter, Kittle’s production disappeared.

One target, zero catches.

In the fourth, it was even less. Zero catches on zero targets.

“We just handled our business and stopped bullshitting, man. That was some BS what we were putting out in the first half. I don’t know what’s going on, but we just had to be better,” veteran Stewart said about what changed with the Broncos’ defense in the second half to slow down Kittle.

If it wasn’t clear in the first half, it was crystal clear in the second half that Kittle was the 49ers’ offense.

In the 30 minutes of play in the second half, when Kittle was nowhere to be found, the 49ers had a pathetic 78 yards of offense, squeezing lemon in the wound of the idea that all it took to beat San Francisco was stopping one player.

A task that proved to be too tall for Denver in the first half.

“He’s going to make his plays. We just beat ourselves. The plays we normally make, we weren’t making them. With a tight end like that, those are the results you get,” Simmons said matter-of-factly in the 6-7 team’s locker room Sunday evening.

To make matters worse, this fifth-round pick in 2017 was drafted one spot after the Broncos drafted fellow tight end Jake Butt.

Butt — who had eternal optimism surrounding him at the start of this season — has played in three career games and has totaled eight receptions for 85 yards to go along with two trips to the injured reserve to rehab two torn ACLs.

On Sunday, Kittle topped 1,000 receiving yards on the season despite playing with three different quarterbacks.

Ouch.

Entering Sunday, with their eyes on the playoffs, the Broncos would have liked to end the season on a seven-game win streak.

But the 49ers’ offense, aka one player, had other things in mind.

On Sunday, George Kittle officially put the Broncos in “must-win” mode for the final three games of the season.