OAKLAND — Ever see a Carr stuck in reverse with the transmission slipping?

It is not a beautiful sight.

Look, we all knew that the Raiders were not in for a swell Sunday afternoon at O.co Coliseum. At this point, you can no longer even call their games against the Denver Broncos an AFC West “rivalry.” A “rivalry” needs competition. The Broncos have won the head-to-head matchup six straight times, by an average score of 36-16. If this were college football, it might be time to discontinue the series.

Yet for Raiders fans in this dismal winless autumn, there has at least been the weekly dose of hope with rookie quarterback Derek Carr. Over the season’s first five weeks, Carr visibly improved game to game, leading up to his four-touchdown passing performance against San Diego in a narrow three-point defeat.

That was Oct. 12. We regret to report that ever since, Carr’s improvement seems to have stultified. Against the Chargers, his passer rating was 107.7. Sunday in the 41-17 loss to Denver, the rating was 68.7, a tick better than his 66.5 rating a week earlier against Seattle.

You can charitably say that Carr has been trending downward. If that matters. Carr prefers not to consult any numbers.

“I don’t know the last time I looked at my own stats,” Carr said after Sunday’s loss. “This is the ultimate team game. All I care about, honestly, is winning.”

That part hasn’t been going so hot for him, either, as you may have noticed.

“He’s learning,” said Raiders offensive tackle Donald Penn. “But the bad thing is, he’s got to learn the hard way.”

Carr does seem to be a solid personality, resilient and all that. He rips off his chin strap in anger when he makes a mistake, so he cares a lot. He plainly has the physical talent to succeed in the NFL and essentially, this Raiders season has become a developmental training camp for Carr.

But if he winds up this season looking worse in December than he did in September, is that the desired result?

Sunday, the “hard way” for Carr consisted of being schooled by Denver’s defense while quarterback Peyton Manning shook off a rocky start to throw five touchdown passes. Carr threw two himself, although one was in garbage time. Carr still somehow took heart.

“The man across the way, he’s one of the best to ever do it,” Carr said, speaking of Manning. “He said it best, experience is the best. If I didn’t play today, I would never gain that experience of the coverages I saw, the different looks that I saw, the way people disguise coverages.”

Fair enough. But the disguises are still fooling him. After going two games without an interception, Carr has thrown four in the past two weeks — and that doesn’t even include the impossibly goofy turnover he helped create Sunday by mistakenly throwing the ball to his own offensive lineman, Khalif Barnes.

The play happened when Carr was feeling heat and suddenly shoveled the ball to Barnes — who turned upfield to run with the ball, then fumbled away the ball to Denver, setting up the Broncos’ third touchdown.

“I don’t know what happened,” Barnes said. “The ball was coming to me, and it was a natural reaction to catch it. I knew I was ineligible, but I just caught the ball and tried to take off. I’ll have to see what happened on film. Things happen so fast in a game.”

Carr’s version of the gaffe was that he’d expected running back Darren McFadden to be an outlet receiver in the spot where Barnes wound up after throwing a block in open space, just beyond the line of scrimmage. Of course, Barnes is 5 inches taller and 100 pounds heavier than McFadden but … all right, so Carr is a rookie.

“All of a sudden I just saw, out of the corner of my eye, this guy standing by himself, facing me,” Carr said. “And so I obviously assumed in my head that it was ‘D-Mac,’ so I turned to go throw it, and in my head as soon as I threw it, I was like, ‘Please knock it down.’ ”

Instead, the Raiders soon were behind 27-10, and the game was all but over except for more Carr “lessons.”

Not all of his slippage is his own fault. Example: In the first quarter under pressure on third down, Carr performed a fine escape job and rolled to his left, then fired a perfect ball to wide open receiver Vincent Brown at first-down distance. Brown dropped the ball.

Afterward, Carr also noted at least one sign of tangible progress in his own mind: A week earlier against Seattle, he made the wrong protection call that led to an interception by Seahawks defender Richard Sherman.

“This week, we saw the look, made the correct call this time,” Carr said. “So, I’m moving in the right direction. But obviously it’s not where I want to be. We all know that.”

“Good things happen to those who wait,” Carr said. “I’m patient.”

It would still be better to see him be patient while shifting back into forward gear. Seven more weeks to see if he can make it happen.

Read Mark Purdy’s blog at blogs.mercurynews.com/purdy. Contact him at mpurdy@mercurynews.com. Follow him on Twitter at twitter.com/MercPurdy.