SANTA CLARA–The Jim Tomsula era started with a bang.

The Chip Kelly era started off on a high note.

The Kyle Shanahan era finally began on Sunday afternoon, and it couldn’t have been more dreadful.

Despite new energy, new confidence, and a new general manager who should help point the franchise in a new direction, the results in Shanahan’s first act as San Francisco’s head coach were hardly different than the ones posted by the most recent, unsuccessful regimes.

The 49ers may have a different quarterback, a completely overhauled roster and a fountain of youth responsible for spraying the team’s depth chart with 14 rookies, but all of that wasn’t enough to create a fresh result, as the Carolina Panthers cruised past San Francisco in a 23-3 final.

Entering week one of the regular season, there were countless reasons to believe that Shanahan’s team would rise to the type of heights that Tomsula’s and Kelly’s couldn’t scale. Of course, for the 49ers’ previous two coaches, victories in the first game of their tenures represented the mountain top, while the remaining games led the 49ers into dark, deserted valleys. Shanahan’s preliminary effort served as a warning sign, a suggestion that to climb more prestigious mountains with greater peaks, San Francisco first has to dig its way out from the bottom of a ditch.

For the first 10 minutes of Sunday’s season-opener, it appeared as though Shanahan had San Francisco walking on flat ground. The 49ers forced a pair of early punts, San Francisco sustained a short drive, and two of its key players, quarterback Brian Hoyer and rookie linebacker Reuben Foster, appeared poised to pace their respective units up the trail to victory.

But in the blink of an eye, an avalanche struck, wiping out any progress the 49ers appeared to be making and forcing them back into a crater beneath the surface.

On San Francisco’s second drive, left guard Zane Beadles lost control of Panthers’ defensive end Wes Horton, who slammed into Hoyer and forced a fumble that changed the course of the game. Carolina recovered the ball, and two plays later, the 49ers lost Foster for the afternoon.

The 31st overall pick in the 2017 NFL Draft, Foster rolled his right ankle attempting to tackle Carolina rookie Christian McCaffrey and needed to be carted off the field. His day was over, and soon after, the 49ers learned theirs was too.

On the ensuing play, Carolina quarterback Cam Newton delivered a 40-yard touchdown pass to Panthers’ wide receiver Russell Shepard, who took advantage of a blown coverage and a missed tackle by San Francisco free safety Jaquiski Tartt.

It was hardly the only mistake the 49ers made that helped the team veer off course, as the offense and defense alike suffered through an afternoon of miscues and slip-ups.

By halftime, the Panthers held a 13-0 lead, thanks in large part to a pair of failed 49ers’ fourth down conversion attempts in Panthers’ territory that led to directly to two Carolina field goals. The failed execution wasn’t limited to fourth down, though, as San Francisco committed a handful of procedure penalties and allowed four sacks while Shanahan struggled to manage the clock in a miserable first half effort.

At least after a halftime break that allowed the franchise to enshrine Tom Rathman in the San Francisco 49ers’ Hall of Fame, Shanahan’s team had the opportunity to start with the ball on offense and open with a clean slate. On the second play of the half, though, the slate was muddied and ruined, as Hoyer threw a terrible interception over the middle that set up a gut-punching 28-yard touchdown drive that put the game out of reach.

San Francisco didn’t put its first points on the board until eight seconds remained in the third quarter, and even Robbie Gould’s 44-yard field goal came after a frustrating moment for Shanahan. Facing a fourth and one at the Carolina 21-yard line, San Francisco took a delay of game penalty after it couldn’t get its fourth down play off in time. That took the 49ers’ offense off the field, and kept San Francisco from having an opportunity to cap off the drive with a touchdown.

While both Tomsula and Kelly began their tenures in San Francisco with blowout wins, Tomsula scoring a 20-3 victory over the Vikings while Kelly capturing a 28-0 takedown of the Rams, the Shanahan era started on a decidedly different track. As Tomsula and Kelly proved, though, it’s important not to judge a book –or a season– by its cover.

Right now, Shanahan’s first chapter reads like a horror story. The 49ers now have 15 games to make sure that narrative changes, and author a comeback tale.