SANTA CLARA >> Even the most wild-eyed optimists are convinced that the 49ers at 5-7 are as good as done.

Probably the only people remaining who believe the 49ers can make something of the 2024 season are a handful of players in the locker room, with tight end George Kittle at the forefront.

“When you lose by 20-plus points, especially when you had expectations of going to the Super Bowl and winning the Super Bowl, it’s not very fun,” Kittle said Thursday. “It’s hard whether you’re a coach, whether you’re a player, whether you’re a fan. It’s a grind.”

Yet Kittle presses on, because as long as there are games to play and NFC West opponents Seattle (7-5), the L.A. Rams (6-6) and Arizona (6-6) are within striking distance with the latter two still on the schedule there’s a belief that that all is not lost.

Do better with turnovers. Do better in the red zone. Stop the run. Get Trent Williams and Nick Bosa back in the lineup . . .

“There are a lot of great players on this team that can make really special plays and all it takes is a spark to get going and after that we can see what will happen,” Kittle said.

More likely, the 49ers will end the season as the NFL’s most disappointing team. That’s where they are right now, and no one else is really close. They’re a victim of their own success, having gone to four NFC title games in five years without claiming the ultimate prize.

How did we get here? Here’s a six-pack of issues/reasons/excuses with the Chicago Bears up next today at Levi’s Stadium:

1. INJURIES >> Every team loses players and preaches the “next man up” mentality ad nauseum, but the 49ers are extreme. Removing last year’s versions of wide receiver Brandon Aiyuk (torn ACL) and Offensive Player of the Year Christian McCaffrey (Achilles tendinitis, PCL strain) from the picture is crippling enough. But there is more.

So much more.

There’s Javon Hargrave, Dre Greenlaw, Talanoa Hufanga, Jon Feliciano with long-term injuries. Lots of others or a game or two. I counted 30 players missing time for more than 120 games. Short-term injuries to Bosa and Williams and even quarterback Brock Purdy.

2. WEEKS 12-13 >> The 49ers went up against legit playoff teams on the road in the last two games and lost 73-20. They were a shell of themselves and coach Kyle Shanahan admitted as much. Green Bay and Buffalo were 9 for 9 in the red zone. The 49ers couldn’t stop the run, a quality that used to be a team staple.

“You can’t get your ass kicked a couple of weeks in a row and not respond,” general manager John Lynch told KNBR-680 Friday. “What I fully expect is that we come out with a response that’s up to our standard and what we expect.”

3. CONTRACT HOLDOUTS >> Aiyuk’s holdout was the body blow, because it was so strange. He pretty much got what he wanted and the offer was on the table for awhile. But Aiyuk waited so long to take it he torpedoed any chance to hit the ground running and rebuild his chemistry with Purdy.

But there was also McCaffrey, who missed much of the offseason program, and Williams, who missed all of training camp. Maybe it factored into their injury issues, maybe not. It’s impossible to know.

Absences set a bad tone for the lead-up to 2024.

4. COACHING >> Pro Football Talk czar Mike Florio is floating the idea that Shanahan could be traded to Chicago. The only way Shanahan is going anywhere is if he wants out. There’s no indication that’s the case. His team had a bad year, so he had a bad year and he’s got a hand in all of it.

There’s no reason Shanahan shouldn’t be scheming up better red zone production than the 50 percent or so they’ve been at all year. Even with all the injuries. Shanahan used to find creative ways to use Deebo Samuel. The 2024 Samuel has been a faint copy of the one in 2021 who earned a huge contract extension.

But Shanahan also directed one of the NFL’s most consistent winners for the last five years. The whole “win the Super Bowl or you’re a failure” mentality is social media and talk radio nonsense.

5. DEFENSIVE INDIFFERENCE >> The fan base wants defensive coordinator Nick Sorensen gone. Last offseason’s dismissal of Steve Wilks looks more and more like scapegoating every week.

Of course, Sorensen hasn’t been working with a full deck, although the 12-men-on-the-field issues were inexcusable. Three starters against Buffalo were starters in last year’s Super Bowl. One of them, Fred Warner, is playing with a broken ankle. Charvarius Ward was in his first game back after a family tragedy. The other is safety Ji’Ayir Brown.

Which isn’t going to stop anyone who plays Madden or looks at All-22 video from skewering Sorensen. I have no idea if he’s a good coordinator. I’m not sure Shanahan knows either based on the the personnel and the pass rush.

6. SPECIAL TEAMS INEPTITUDE >> Fraught with disaster from the beginning. Who else is so bad at defending kickoffs they lose two kickers in two weeks? There have been missed field goals, coverage disasters and not much in the way of returns. Samuel finally started to break loose against Buffalo and lost a fumble.

This is as much on Shanahan as it is coordinator Brian Schneider, who could pay with his job. The organizational philosophy is simply to break even on special teams. Don’t worry about winning the game, just don’t lose it.