Jayne Kamin-Oncea / Stringer

LOS ANGELES — The 49ers fell to the Los Angeles Chargers, 29-27, Sunday afternoon. After leading 14-0, the Chargers slowly cut the deficit and took the lead in the third quarter. The 49ers battled back, but a couple costly turnovers squandered their chances at a win, putting them at 1-3 on the year.

Here are five thoughts from the two-point loss.

The 49ers overcame injuries and poorly timed mishaps to give themselves a chance

The trajectory of the 49ers’ 2018 season changed dramatically when Jimmy Garoppolo went down with a torn ACL last Sunday, ending his season just three games in. They entered Sunday’s matchup at Los Angeles without their starting quarterback, running back (Jerick McKinnon), and best cornerback (Richard Sherman).

The laundry list of injuries grew Sunday. (The 49ers have not disclosed the severity on any of their players’ injuries.)

First, Dante Pettis injured his knee during a punt return in the first quarter. It looked as if multiple Chargers defenders rolled up on Pettis’ left leg. He did not return.

In the second quarter, Joe Staley went down with a knee injury. He also did not return.

Among the 49ers players who were injured but returned to the game were Weston Richburg, C.J. Beathard, Solomon Thomas, and Mike McGlinchey.

Couple the injuries with mental mishaps and Garrett Celek’s crucial dropped pass, which devolved into an 86-yard interception return, and the 49ers didn’t help themselves. Yet they stayed in the game and matched each Chargers run with one of their own.

C.J. Beathard looks much improved

From the looks of Sunday, C.J. Beathard has improved from his rookie season in just about every facet. In his first game since replacing Garoppolo, Beathard was terrific, converting third downs, extending plays with his legs, and delivering challenging throws in the face of pressure.

He completed 23 of his 37 passes for 298 yards with two touchdowns and two interceptions.

One of Beathard’s most impressive drives was San Francisco’s third of the game. He completed four of five passes on third down. He also helped force a defensive holding on third down. The 49ers methodically moved the ball, using 21 plays and nearly 11 minutes to give their defense plenty of rest. While the drive ended with a field goal, it encapsulated Beathard’s progression and showed he is capable of slowly picking apart an NFL defense.

He also hit the big play.

As the third quarter progressed, the 49ers were in danger of letting the game slip away as they trailed by nine points. But after Matt Breida’s two-yard run, Beathard hit tight end George Kittle up the seam, and he outran the Chargers defense for an 82-yard touchdown, cutting the Chargers’ lead to 26-24.

Beathard’s day ended sour when Chargers safety Derwin James sacked him, altering the throw. He was intercepted with fewer than three minutes remaining in the game.

Despite his two turnovers, neither of which were egregious, Beathard’s opening performance should inspire optimism moving forward.

Garrett Celek’s drop was the most important play of the game

The Chargers had scored 17 straight points early in the third quarter, and the momentum had shifted in their favor. The 49ers quickly charged back. Beathard completed four straight passes on the ensuing drive, moving the ball 82 yards in about a one-minute span.

But the drive went to waste when tight end Garrett Celek dropped a ball he should have caught near the goal line. Chargers cornerback Trevor Williams scooped the interception and ran it 86 yards to the 49ers’ two-yard line. In a two-point game, that play was a major factor in swinging the final result.

George Kittle is blossoming into a top-tier tight end

By the numbers, Kittle had a historically great rookie season, even if his numbers appear somewhat modest. He caught 43 passes for 515 yards with two touchdowns, which is the best rookie production ever for a tight end drafted in the fourth round or later.

Kittle looks like a potential Pro Bowler through four games this year.

Kittle led the 49ers in every receiving category Sunday, catching six of eight targets for 125 yards and a touchdown. Prior to his 82-yard score, the longest play of his career was previously a 44-yard catch.

Kittle leads the 49ers with 20 catches for 316 yards through four games. He is on pace for 72 catches and 1,264 yards over a full 16-game calendar.

He may be the only 49ers receiving option whose production does not curtail with Garoppolo’s absence. Kittle played with Beathard at Iowa. Their connection continues to grow.

Mental mistakes and missed tackles continue to plague the defense

The 49ers entered Sunday allowing touchdowns on nearly 67 percent of opposing red-zone trips. They allowed just two touchdowns on five red-zone trips Sunday, but both seemed to be avoidable.

On third and goal in the second quarter, Ahkello Witherspoon blew his coverage, allowing Chargers tight end Antonio Gates to run free for an easy touchdown catch. Gates ran a crossing pattern, and Witherspoon and Foster didn’t account for him. The closest defender to Gates was 13.62 yards away, according to NFL Next Gen Stats.

Fast forward to the third quarter. On another third and goal, Chargers quarterback Philip Rivers found running back Melvin Gordon, who curled his route near the goal line, for a touchdown. The 49ers’ zone coverage was too soft, allowing for Rivers to take his time before finding the open Gordon.

The 49ers had just one sack Sunday. The lack of pass rush continues to put stress on the secondary to be disciplined in its assignments for extended periods. For a young team still learning how to play together, these mistakes and miscommunications are growing pains.

Last week, they had 17 missed tackles. They entered Sunday leading the league with 43 missed tackles through three weeks. They fixed the issue in the first half Sunday, but it resurfaced in the second half. Those missed tackles fueled Los Angeles’ comeback and played a part in the loss.