Why Raiders game Sunday could be key to Chargers’ entire season

The most prolific receiving day in the career of the most prolific receiver in franchise history included an all-time, league-stopping highlight that was the exact opposite of receiving.

That’s how complete and overwhelming of a performance Keenan Allen produced last weekend in Minnesota.

All those catches (18 of them, setting team and personal bests) and yards (215, also a career high) had to share the shine with Allen’s 49-yard touchdown pass to fellow wideout Mike Williams.

“I’m excited, nervous,” Allen said a few days later recalling the feelings that welled up inside him when the trick play was called. “ ‘Don’t you mess this up, Keenan.’ ”

Allen most certainly did not, firing a deep pass to a wide-open Williams with form that later would be publicly admired by Justin Herbert, a quarterback with exquisite enough skills that he passed for a career-high 405 yards against the Vikings.

“That’s why I got the job,” Allen said. “I look good doing it.”

Yes, the mood was jovial in the aftermath of the Chargers’ first victory, a win that might not have technically saved their season but for sure allowed them to exhale and feel the warmth of relevance again.

Now all they have to do is repeat the result — Sunday against Las Vegas at SoFi Stadium — or face the real possibility that their enormous first victory wasn’t all that enormous after all.

Sitting at 1-2 and barring a tie, the Chargers will enter their off week at 2-2 or 1-3, the difference particularly significant given that, upon their return, they play home against Dallas and then travel to Kansas City.

The Chargers could win Sunday, take their mandated break, come back and play very well and still be 2-4. As grave as that might sound, it’s probably best not to consider the ramifications of being 1-5.

Believe it, as much as the Chargers couldn’t afford to lose to the Vikings, they equally can’t afford to lose to the Raiders before a crowd that will be one in passion but split in allegiance.

Even matched against a Las Vegas offense that has scored only five touchdowns to date, the Chargers can’t count on anything being easy, because nothing ever seems to be easy for this team.

Including the postseason, 12 of the last 14 games for the Chargers have been decided by one score. They’re 5-7 during that stretch and had dropped four one-possessions decisions in a row before winning 28-24 at Minnesota.

They also still haven’t sorted out their defensive issues despite consecutive late goal-line stands that clinched their victory last Sunday. The dramatic breakdowns — brutal blown coverages, killer third-down penalties — remain far too consistent.

The Raiders’ uncertainty at quarterback in advance of Sunday offered little solace to a defense still last in the NFL against the pass and readying for Davante Adams, a three-time All-Pro receiver who reached that status last year in part by twice shredding the Chargers.

The Raiders' Davante Adams (17) runs after a catch against the Chargers' Asante Samuel Jr. last season.

The Raiders’ Davante Adams (17) runs after a catch against the Chargers’ Asante Samuel Jr. last season. The Chargers have been allowing long pass plays to star receivers so far this season.

(Matt York / Associated Press)

Quite simply, win or lose Sunday, the Chargers’ record isn’t going to make any difference unless their defense can find its way. If the group continues to play as it has to this point, the Chargers aren’t going anywhere anyway.

Offensively, there’s also an issue to consider after amassing 475 yards in Minnesota. Williams suffered a season-ending knee injury against the Vikings, forcing the Chargers to turn to rookie Quentin Johnston.

A first-round pick at No. 21 overall, Johnston had been used part-time through three weeks but now is in line to see an increased role — helping replace Williams while discouraging defensive backs from congregating around Allen.

“We just need him to be him, be the guy that we drafted,” Allen said. “We don’t need no more. We don’t need no less. When you get drafted [with] first-round talent … we need first-round talent.”

Johnston struggled with drops at times in training camp and the preseason, and continues to pursue the trust of Herbert and his coaches. He enters Sunday with five catches for 26 yards.

At Texas Christian, Johnston became a star mostly lining up on the same side of the formation and in the same spot on every play. He admitted Wednesday that he has had a difficult time with the Chargers “juggling all the plays” but said he’s feeling more comfortable.

Back in training camp, wide receivers coach Chris Beatty talked about Johnston’s transition to the NFL hinging on his ability to play without being a drag on the offense.

“I don’t want Justin looking at me like, ‘Why’d you send this guy in the game?’ ”Beatty said. “There’s a process to knowing, ‘Hey, you’re not going to slow down the offense. Once we know that you’re not going to slow us down, then we can put you in with Justin and he feels good about it.’ ”

Coming off a game during which he was so many things, Allen said he likely will add big brother to his list this week, double-checking the fine print with Johnston to help avoid catastrophe and free up the rookie.

“Every time we break the huddle I’m probably going to tell him what he got just so there’s no misunderstandings, no questions so he can just go play fast,” Allen said.

Sounds like a solid enough idea, the Chargers placing a young receiver in the team’s best hands.