Kurtenbach: Coaching, QB failures have 49ers sliding down NFL pecking order

SANTA CLARA — There was a point this season when the 49ers looked unbeatable. Now, it’s hard to remember how they ever won a game.

Humbling comes easy in the NFL. It arrived fast for the 49ers.

After starting the season with five straight wins — four of them blowouts — the 49ers will head into their bye week with a three-game losing streak, a second-place standing in the NFC West, and plenty of bad vibes.

And after Sunday’s 31-17 loss to the Bengals, fans should be worried that the 49ers’ best football is behind them this season.

Not only is this team falling apart physically, but the Niners also have serious problems at the top of the football operation.

The two core tenets of winning in the NFL are solid coaching and prudent quarterback play.

If your team has both, you will consistently be one of the NFL’s better teams.

But the last three weeks — all losses — the 49ers have lacked both.

And there’s no guarantee the solid coaching or quarterback play returns after the bye week, either.

The book is out on first-year defensive coordinator Steve Wilks. It’s not a complicated read, either.

Wilks came to Santa Clara to take command of the NFL’s best defense this past offseason. Wilks is the Niners’ third defensive coordinator under head coach Kyle Shanahan, but unlike Robert Saleh, who built the defense, or DeMeco Ryans, who was on Salah’s staff, Wilks is the first with an outsider’s perspective.

Wilks didn’t change much with the 49ers’ defense in the first few weeks. He said he wanted to feel things out, so he called simple, high-school-level plays and allowed the elite players on the field to control the game.

That worked in the early weeks of the season when opposing offenses were in a stage of self-discovery.

But we’re at the mid-point of the season now, and opposing offenses know what they can and cannot do. Just as important — they know what the Niners can and cannot do.

Wilks is still yet to change anything.

The lack of ingenuity or creativity was glaring when the Niners lost to the Browns, unavoidable when they lost to the Vikings the next week, and downright comical on Sunday against Cincinnati.

Against a near-exclusive diet of vanilla zone defense, Bengals quarterback Joe Burrow completed 28 of 32 passes Sunday. Burrow is a great quarterback, but I’m not sure he could complete 87 percent of his passes without a defense on the field.

Wilks put his defense in position to fail snap after snap, and the players on the field followed through. Wilks was timid in the press box — that’s where he calls the game, as opposed to the Niners’ last two defensive coordinators — and his team played timidly a few hundred feet below, missing tackles and allowing easy passes and runs to become big gains.

Cincinnati had a game’s worth of first downs in the first half. When the Niners threatened to make a game out of it in the second half, the Bengals immediately answered with easy scores.

It shouldn’t be this easy. Not when the defense has two of the best players in the game and plenty of talent around them.

Shanahan gave Wilks a vote of confidence after the game, but over the next two weeks, something must change. After the Niners’ defensive coaching staff was plundered amid Saleh and Ryans’ exits over the last few seasons, there’s no obvious choice to replace Wilks on this coaching staff. That’s part of the problem, and it’s up to him to fix it, as Shanahan — who runs the team’s offense — outsources the defense.

And Wilks has no track record with this team to suggest he can fix what ails this defense.

What a waste of talent.

But Wilks’ failures don’t exonerate Shanahan or quarterback Brock Purdy, either.

The partnership that once looked unbeatable — they won their first 13 games together — has looked lost the last three weeks as injuries have sidelined two of the team’s three best offensive players.

Without do-it-all wide receiver Deebo Samuel and All-Pro left tackle Trent Williams, both injured in Cleveland, the 49ers have only mustered 17 points per game — a far cry from the 30-plus they were averaging the first five games of the season.

Like on defense, the Niners are becoming predictable on offense. Shanahan is still calling some big-gain plays here and there, and Purdy is still making big-time throws and extending plays with his feet, but the Niners’ offense can no longer effectively run the ball behind a poor offensive line, and Purdy is now turning the ball over at a losing clip.

Purdy started the season with nine touchdown passes to one turnover in the Niners’ first five games.

In the last three weeks, he has five interceptions to three touchdown passes. On Sunday, he threw interceptions on back-to-back plays in the fourth quarter, burying San Francisco.

Purdy isn’t a scrub — he’s still the best quarterback Shanahan has started in San Francisco — but in the last three weeks, with the defense faltering, the 23-year-old has been put in a position to win or lose the game for the Niners.

He’s not that kind of quarterback. Not yet. Perhaps not ever.

Sure enough, Purdy has lost all three games, and his level of culpability has increased with each passing (or, rather, intercepting) game.

It’s on Purdy not to turn the ball over and Shanahan not to put him in positions to make those mistakes moving forward.

Early in the season, both were doing their jobs. Until that competency returns, the Niners cannot be considered a title contender.

The tragic part is that this team has the talent — even with key injuries — to be one of the NFL’s best. It might even be the best team in the league. That 5-0 start wasn’t a fluke.

But right now, the 49ers’ failures at the three most important positions in the game, head coach/offensive coordinator, defensive coordinator, and quarterback — paired with key injuries — have tightened the margins between them and the rest.

The three straight losses have made these Niners look like frontrunners, and they are now 0-37 when trailing by eight or more points in the fourth quarter under Shanahan.

They have two weeks to get healthy, determine what changes must be made, and make them.