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The 49ers lost their season opener Sunday to the Minnesota Vikings, 24-16. The defeat provided the first glimpse of a San Francisco squad that has undergone plenty of change since this time last year.

Here are the positives and negatives from the Week 1 loss.

POSITIVES

Fred Warner

Warner showed why the 49ers selected him in the third round of April’s draft. He was everywhere on Sunday, shooting running gaps and tracking down pass-catchers. He was advertised as a rangy, sideline-to-sideline prospect with cornerback skills. He showed that, while also summoning his inner Reuben Foster by blowing up running plays.

Warner amassed nine solo tackles in the first half of his NFL debut. He finished with 12 total tackles, 11 of which were solo. He also forced a fumble, popping the ball loose from Vikings running back Dalvin Cook, in the second quarter, and Richard Sherman recovered.

It was a much-needed performance as Foster serves his two-game suspension and Malcolm Smith nurses a hamstring injury that sidelined him Sunday. Brock Coyle also suffered a concussion in the game, shrinking the linebacking corps even more.

Warner has become indispensable. He was one of the best players on the field in Week 1.

DeForest Buckner

The lack of pass rush was one of San Francisco’s biggest weaknesses last year. The 49ers had three sacks Sunday, all of which were yielded through Buckner.

Buckner posted 2.5 sacks in the loss. He shared the third with Ronald Blair.

Buckner had just three sacks all of last year, though his 19 quarterback hits led all interior linemen. Buckner is a legitimate Defensive Player of the Year candidate in his third season.

Dante Pettis

Pettis, San Francisco’s second-round pick, hauled in the team’s first touchdown of the 2018 season in the third quarter. It was also his first NFL catch. Garoppolo avoided pressure, rolled to his left, and delivered a strike to the toe-tapping Pettis.

Big-time play here from Jimmy G. Dante Pettis' first NFL catch is a touchdown. pic.twitter.com/UarFPnu64Z

— Brad Almquist (@bradalmquist13) September 9, 2018

In the fourth quarter, Pettis shook Vikings cornerback Mike Hughes on a corner route, then turned the completion into a 39-yard gain. Pettis finished with two catches for 61 yards on the day.

Pettis’ footwork and fluidity translated from the preseason into the regular season. He looks to be a key to this offense, especially if Marquise Goodwin’s quad injury requires him to miss time.

George Kittle

George Kittle missed nearly all of the preseason with a separated shoulder, but he was Garoppolo’s favorite target Sunday. The second-year tight end logged five catches for 90 yards. He also dropped what would have been at least a 30-yard gain on a floating throw over his shoulder.

Kittle was the beneficiary of a couple of Kyle Shanahan’s class play action calls on early downs.

Kyle Shanahan summed up in a drive. Four consecutive play actions result in three completions and a pass interference penalty. #49ers got on the board with a field goal. pic.twitter.com/SNZpxHMFbf

— Brad Almquist (@bradalmquist13) September 9, 2018

Last year, Kittle caught 43 passes for 515 yards and two touchdowns. He jelled with Garoppolo upon his arrival, and it seems that partnership is only flourishing in their second full season together.

NEGATIVES

Red zone offense

We identified the red zone offense as one of the important dynamics to watch Sunday. That’s because the 49ers struggled immensely in that department last year. The red zone offense improved when Garoppolo took over the offense, but the problem resurfaced this preseason when the 49ers starters converted just one of their five red zone trips into touchdowns.

Garoppolo went 15 for 33 with 261 yards, one touchdown, and three interceptions. Two of his turnovers were poor decisions met by poor throws, but one of them was due to a miscommunication with wide receiver Kendrick Bourne, who ran the wrong route. It was Garoppolo’s worst performance as the 49ers quarterback, and his first loss as a starter, but he still moved the ball into Minnesota territory five times.

On one of San Francisco’s most promising drives, Alfred Morris fumbled on the goal line in the second quarter. In the third quarter, Garoppolo lobbed a perfect throw to Pierre Garcon, but he failed to secure the contested catch.

The Vikings, conversely, punched their lone red zone opportunity in for a touchdown. Kirk Cousins was surgical in 49ers’ territory, finding Kyle Rudolph in the back of the end zone for a touchdown. In the second quarter, Cousins threw a perfect pass to Stefon Diggs up the sideline past Ahkello Witherspoon for a 22-yard score.

The 49ers offense had little problem moving the ball in the second half. But they had issues maximizing their drives.

Rushing attack

Earlier this week, Shanahan said losing Jerick McKinnon “changes things pretty drastically.” That shifted the rushing responsibility to Matt Breida and Morris.

On Sunday, Breida had 11 rushes for 46 yards, and Morris had 12 carries for 38 yards.

The rushing attack was never truly established, though there were spurts of promise. Morris’ fumble on the goal line ended up being a huge play in a one-possession game.

The 49ers were forced to throw as they trailed by 18 points and attempted to mount a fourth quarter comeback. But they will need more production from the rushing attack, which was neither great nor horrible, moving forward.

Injuries

The severity of Goodwin’s quad injury is important to monitor. Coyle’s concussion exacerbates the lack of depth at linebacker.

But the right guard spot took the biggest hit.

Starter Mike Person suffered a foot injury in the first quarter and did not return. Joshua Garnett replaced him, then sustained a foot injury of his own shortly after. Rookie Mike McGlinchey was forced to play right guard, and Garry Gilliam moved to right tackle. It was the first time in McGlinchey’s life that he played right guard, and it came in his NFL debut.

The right guard spot was the lone position without a clear-cut starter entering training camp. Person won the job with consistency, as Garnett and Jonathan Cooper, who was ultimately cut, dealt with knee injuries. Garnett missed all of last season with a knee injury, too. He has struggled to stay on the field since the 49ers drafted him in the first-round in 2016.

With Erik Magnuson still recovering from a hamstring injury, the right guard outlook has become a concern.