ALAMEDA, Calif. (AP) — A season that started with the highest expectations in Oakland is ending with a losing record and many questions about how things went so wrong for the Raiders in 2017.

With an emerging star at quarterback in Derek Carr returning with most of the major pieces from one of the league's most dynamic offenses and some high draft picks to boost what was an opportunistic defense, many expected the Raiders to build on last year's 12-win campaign and become a contender to challenge New England in the AFC.

Instead, the offense took a major step back after a switch at coordinator from Bill Musgrave to Todd Downing, the draft picks never really contributed on a defense that was poor until a late-season change in coordinator, and the Raiders (6-9) head into Sunday's season finale at the Los Angeles Chargers with questions about how much change is necessary to right the ship in Oakland.

"When we show flashes of what we can be, then everyone is like, 'Oh, there it is,'" Carr said Wednesday. "But then we weren't consistent enough. We're not consistent enough all year, especially in the details of our assignments. That's one area that has to and will be cleaned up."

Downing is expected to be replaced after overseeing an offense that regressed, and the changes on the coaching staff could run even deeper with coach Jack Del Rio's status even in question despite signing a four-year extension last offseason.

Del Rio praised Downing on Wednesday but there still might need to be a change.

"A lot of things have gone on in a negative direction. But I do know the guy is super bright," Del Rio said. "He's going to be a really good coach in this league. I believe in him. Those are not things that people want to hear right now because the reality is we've underperformed offensively this year. So naturally there's going to be those kinds of questions."

That the Raiders would be facing these types of questions in Week 17 rather than gearing up for a playoff run seemed far-fetched way back in September when they opened the season with two straight wins.

But the problems that arose during the four-game losing streak that followed and then again during a late three-game skid that officially ended the team's playoff hopes even before Monday night's 19-10 loss in Philadelphia were put in place far earlier.

Despite a 12-4 record last year, Del Rio decided to make a change at offensive coordinator from Musgrave to Downing. The hope was Downing's strong relationship with Carr would lead to even more improvement from the quarterback who was given a $125 million contract in the offseason.

Del Rio then decided to stick with defensive coordinator Ken Norton Jr. despite struggles on that side of the ball. Former Chargers coordinator John Pagano was brought in as a defensive assistant to improve the communication on the back end but that didn't materialize and Norton was fired after 10 games.

The defense has dramatically improved the past five weeks with Pagano calling the plays and the Raiders won those first two games against backup quarterbacks from Denver and the New York Giants to get back to .500 and playoff contention, but the offense fell completely flat from there.

Carr has looked little like the MVP candidate he was a year ago when he engineered seven fourth-quarter comebacks and showed some gun-slinging traits of his idol Brett Favre.

Whether it was the new coordinator, last year's broken leg or the broken bones in his back suffered in Week 4, Carr's propensity for getting rid of the ball quickly became even more pronounced this year as his yards per attempt, touchdowns and big plays took a notable drop. That led to Oakland becoming rather pedestrian on offense despite having three Pro Bowl linemen and getting solid play from running back Marshawn Lynch.

The Raiders failed to score more than 17 points in nine of their 15 games — all of their losses — as the offense was unable to carry the team this year.

The problem was especially stark the past three weeks when the team's playoff dreams died. Oakland was held scoreless for the first 51 minutes in a 26-15 loss at Kansas City that essentially ended hopes of a division title. Carr then lost a fumble while stretching the ball out for a potential winning score in the final minute of a home loss to Dallas that all but ended the team's wild-card chances.

The unit then might have hit rock bottom this past week with five second-half turnovers in the loss at Philadelphia on a night when the defense completely shut down Nick Foles and the Eagles offense.

But by then it was too late to save a season that had already turned to disappointment.

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