San Francisco 49ers quarterback Colin Kaepernick, with a rare clean pocket in which to set up and throw, reared back and fired.

Thirty-eight-year-old Oakland Raiders safety Charles Woodson, Kaepernick's apparent target on the play, enveloped the ball—then popped up, ball triumphantly raised in the air. With that unforced error, Kaepernick's second turnover of the game, a black curtain fell on the Harbaugh era in San Francisco.

Sure, head coach Jim Harbaugh's exit has been widely discussed since he and the team failed to come to terms on an extension before the start of the season.

Yeah, that talk has amplified since Thanksgiving night, when 49ers owner Jed York tweeted their lopsided loss to the division-rival Seattle Seahawks was "unacceptable."

Speculation only intensified as the University of Michigan's season fell apart. Harbaugh's been connected to his alma mater's coaching job for as long as he's been coaching, but his upcoming availability and Michigan's historic tailspin dovetailed perfectly.

Per NFL Media's Ian Rapoport, Michigan reached out to Harbaugh some time before the 49ers' embarrassing 24-13 loss to their Bay Area foes. Rapoport's source told him "U-M left convinced he wanted to be an NFL coach." Anyone who's been watching the 49ers knows Harbaugh won't be an NFL coach for much longer—and his players' performance is pushing him out the door.

Have the 49ers quit on Harbaugh? Bleacher Report's Matt Miller and Chris Simms don't think so:

If they haven't quit on Harbaugh, though, something else has gone horribly wrong.

In each of Harbaugh's first three seasons, the 49ers reached the NFC Championship Game. The team was a reflection of him: fiery, physical and obsessed with winning. The 49ers punished opponents on both sides of the ball; their dynamic edge players made game-changing plays in the space opened up by their dominant fronts.

On offense, the power rushing of Frank Gore was the foundation of a devastating read-option run game and play-action pass game. On defense, Justin Smith and a mind-bogglingly deep, talented linebacking corps terrorized running backs and quarterbacks alike.

Early on in 2014, though, there were troubling signs that things were different.

In their first three preseason games, the San Francisco offense was blown up, plowed under, spun in circles and tied in knots. The 49ers were outscored 57-3 in the first two preseason games, and their first-team offense didn't put up a single preseason touchdown.

Neither the loss of center Jonathan Goodwin to free agency nor the contract holdout of guard Alex Boone could entirely explain the dramatic falloff in physicality—and when the scores started counting, nothing changed. Even Boone's return didn't restore order.

The 49ers have limped through a deeply disappointing season. Their seven wins include some needlessly close shaves: In November, they beat three teams with a combined 12-27 record by just 13 total points. Their six losses now include some real stinkers: A 28-20 loss to the Chicago Bears, a 13-10 stinker against the St. Louis Rams and the "unacceptable" Thanksgiving loss.

If that was unacceptable, this was unthinkable. 

The Raiders came into the game 1-11. They ranked dead last in the NFL in scoring offense, per Pro-Football-Reference.com, and third worst in scoring defense. They had just been demolished 52-0 by the then-4-7 Rams.

The Bay Area rivalry hasn't meant much during Oakland's long, futile search for a post-Gruden identity. But the 49ers, who expected to be challenging for the Super Bowl yet again, losing to the Raiders? The Raiders?

The lost ship of fools desperate to escape their crumbling, sewage-clogged stadium? The franchise whose free-agency gaffes were the NFL's biggest offseason punchline? The team whose head coach got the ax before September was out? Yes, those Raiders.

There was rookie quarterback Derek Carr, slicing through the vaunted 49ers defense at will. He completed an incredible 78.6 percent of his passes. He averaged a whopping 9.07 yards per attempt. He connected with seven different receivers, threw touchdowns to three different receivers—including offensive tackle Donald Penn—and never turned it over.

The Raiders defense boarded, shanghaied and sunk the 49ers. It sacked Colin Kaepernick five times, picked him off twice and held him to just 5.27 average yards per attempt and a solitary touchdown. Receivers Michael Crabtree and Anquan Boldin and tight end Vernon Davis were the only 49ers who caught more than one pass. Kaepernick force-fed 15 of his 18 completions to that trio. None cracked 60 yards receiving.

Despite gashing the Raiders for an average 5.25 yards per attempt, Gore was given just a dozen touches. Kaepernick's three scrambles for 26 made up nearly all of the rest of the 49ers' 97 rushing yards.

Offensive coordinator Greg Roman, once thought one of the NFL's brightest minds, abandoned the run against a defense ranked sixth-worst in rushing defense. The result: a Gatorade shower for interim head coach Tony Sparano.

Back in late September, NFL Network analyst—and former San Francisco 49ers cornerback—Deion Sanders made waves when he reported 49ers players "want [Harbaugh] out," per NFL.com.

As rocky as the season's been, could that really be the case? Have the 49ers been coasting by for their lame-duck coach? As Sanders pointed out, it sure seems that way from their level of play.

The 49ers used to be an extension of their smart, tough, don't-take-any-wooden-nickels head coach. In November, though, stalwart left tackle Joe Staley gave us a window into the veterans' attitude this season. Per Grant Cohn of The Press Democrat, Staley blamed the 49ers' disappointing offense on "penalties, dumb blocks, dumb techniques and dumb schemes."

Per Ryan Sakamoto of NinerFans.com, Staley later walked his comments back a bit:

His retraction, though, is belied by his actions—and the actions of the rest of the 49ers offense. They don't look like they believe in the game plan. They don't seem to be giving it their all. Somehow, one of the smartest, toughest teams in the NFL has become one of the dumbest. 

Somehow, it's much less than the sum of its parts.

Between Kaepernick, Gore, Boldin, Crabtree and Davis, the 49ers have the same skill-position crew that's finished 11th in scoring offense each of the last three seasons. Dropping from 10th in their pass-blocking grade, per Pro Football Focus (subscription required), to 18th has fueled a massive regression by Kaepernick—and the 49ers ranked 25th in scoring before being held to 13 points by the Raiders.

Have the 49ers tuned out Harbaugh's spittle-flecked tirades? Is Roman beating himself with too-smart-by-half game plans? Is Kaepernick incapable of seeing a lot of the field fast enough to beat teams with his arm? Has the tension between the head coach and front office destroyed the locker room chemistry?

We don't know the answers to each of these questions individually, but we know beyond a shadow of a doubt what we saw on Sunday, December 7: the sealing of the Jim Harbaugh fate in San Francisco.

Harbaugh might not be fired in the following hours. He might not be fired in the following days. He might not quit to take the Michigan job. He might not be gone when the clock strikes midnight on December 28. 

As clearly amazing as his accomplishments in San Francisco have been, though, there's only one thing clear about the 49ers right now: Harbaugh won't be coaching them in 2015.