• The Chargers are in desperate need of a reboot, but trading away Justin Herbert — even for three first-round draft picks — won’t be part of the team’s plans.
• Former NFL team executive Joe Banner believes there is “zero” chance of the Chargers parting ways with Herbert via a trade.
• Herbert has not played well in Mike McDaniel’s disastrous offense, but there’s still too much upside with Herbert for the team to seriously consider trading him.

This is not the perfect spiral the Chargers were expecting. It’s a downward one. Week after week, loss after loss.

They are 0-6 for the first time since 2000, back when Jim Harbaugh was one of their quarterbacks, not their head coach. So even though they’re rested after a week off, they’re also on edge heading into Sunday’s game against the Rams.

On the outside, speculation has been swirling for weeks about what the sinking franchise can do — not so much to stop its current slide, as the season is already shot, but moving forward beyond this year. So far, the switch to Mike McDaniel as offensive coordinator has been disastrous, and there’s even conjecture the team could look to trade quarterback Justin Herbert, who has gone eight consecutive games with at least as many interceptions as touchdowns in each.

The franchise is built around Herbert, mind you, and Harbaugh has predicted he’ll one day be regarded as the best quarterback in NFL history. So the notion of trading him is beyond blasphemous.

It shouldn’t happen, and it won’t happen.

That’s not to say clubs don’t make dramatic and surprising moves. With the trade deadline a week from Tuesday, the 2-5 Indianapolis Colts are already starting to disassemble their roster. Last week, they traded eight-time Pro Bowl guard Quenton Nelson to Seattle, and dealt star defensive tackle DeForest Buckner back to San Francisco, the team that drafted him.

But part ways with Herbert, even for three first-round draft picks, as the water-cooler talk has contemplated? Pure fantasy football.

Say that’s the going rate for a franchise quarterback, even if those transactions seldom happen. If history is a guide, three first-round picks translate into about 1½ quality starters. Not Pro Bowl players, but guys who can reliably crack the starting lineup. Quarterback is the hardest piece to find, and maybe the most difficult position in sports. So trading away a quarterback you believe in is crazy.

“If you said, ‘Do I think there’s a possibility of trading that quarterback?’ I would say zero,” said Joe Banner, who helped build some of Andy Reid’s outstanding Philadelphia Eagles teams. “I literally would say zero, not even like small.”

Banner knows personnel, and he knows Harbaugh. In fact, when Banner was chief executive of the Cleveland Browns more than a decade ago, he reached an agreement with the 49ers to trade draft picks for Harbaugh, then San Francisco’s coach. The last step was Harbaugh’s approval. He declined.

Banner, who said he studied Harbaugh “quite extensively” before attempting that trade, said of the coach: “I can’t even imagine [trading Herbert] is a thought in his head.”

“My bet is Jim doesn’t think he’s that far from having a massively better team, and is more interested in having enough money or draft picks to strengthen those lines than he is even contemplating moving a quarterback, even if somebody was willing to give up three first-round picks.”

What’s clear is the current situation isn’t working. Herbert is taking a beating, just as he did last season, and he looks far less confident than he has in years past. Whereas his interceptions in past seasons often came when he over-trusted his arm and tried to squeeze the ball into a tiny window, or the football was tipped, some of his picks this year appear as if he’s flatly misreading coverages.

During the bye week, he and McDaniel watched video for a total of four hours together over two days. Harbaugh, who after the Week 6 loss to Kansas City wouldn’t commit to what role McDaniel would play, now says the coordinator will continue to call plays.

“The thing you want to do when things aren’t working is to throw it in a trash bin and just do something else,” McDaniel told reporters this week. “But you take the time to do due diligence.”

It should be noted there’s no sure-thing Andrew Luck in the upcoming quarterback draft class. The most intriguing prospect is Oklahoma State’s Drew Mestemaker, who wasn’t the starting quarterback of his high school team. He’s a great story, but not a guaranteed answer for any NFL team.

Herbert’s toughness is not in question. Since the start of last season, no quarterback has been sacked as many times. He’s at 75 sacks in 22 regular-season games, and the next closest is New England’s Drake Maye at 60.

There’s no question that Herbert has not played well. But he’s also missing several key pieces, including starting tackle Rashawn Slater, and a banged-up cast of receivers and tight ends. Ladd McConkey would be a good No. 2 receiver and an excellent No. 3, but with him as a No. 1 and precious few sure-handed options around him ... the Chargers are undeniably undermanned.

Herbert is robotic with the media, particularly after games, and is quick to blame himself when anything goes wrong. Although accepting that blame might be honorable, McDaniel said it’s becoming a problem.

“He tends to put the burden and the blame all on his shoulders, and that’s not fair or realistic,” the coach said. “He doesn’t need to shoulder the blame of the failure of the complete result.”

There is a number that haunts Herbert, and has loomed larger by the year. He’s 0-3 in playoff games, and really only played one good half in those postseason appearances, the first two quarters in Jacksonville almost five years ago, before the Chargers blew a 27-0 lead.

The quarterback on the opposite sideline Sunday can sympathize with those postseason frustrations. Matthew Stafford spent 12 seasons in Detroit and never won a playoff game, going 0-3 in the postseason. Then the Rams traded for him, and he won a Super Bowl in his first season with his new team.

The Chargers aren’t going to let Herbert go. No coach preaches competition more than Harbaugh. Trading away the quarterback is the quintessential wave of the white flag. Of course, that won’t quiet the chatter.

“If I were an NFL general manager, I would go get Justin Herbert and pay any price,” said Rick Neuheisel, the longtime coach and current college football analyst. “The guy’s sensational. I think he’s brilliant.

“He would be the guy I’d go get immediately before I draft any of these other guys, because I already know what he can do. I’d be thinking, I’m going to have him through his glory years. ... You tell Justin I’d take him in a New York second.”

Like his team this season, Herbert isn’t going anywhere.