Three quick takeaways from 49ers' 28-18 loss to Cardinals

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SANTA CLARA -- Things couldn't have gone much worse for the 49ers on Sunday, and they now run the risk of seeing their season quickly fall apart.

Their top running back exited in the first quarter with an ankle injury. The 49ers committed five costly turnovers and didn't generate any takeaways in return. And even their ultra-reliable kicker also had one of those days.

Robbie Gould and the field-goal unit aborted an extra-point attempt in the first quarter. Later, Gould’s streak of consecutive field goals ended at 33 when he pushed a 45-yarder wide.

The previously 0-3 Arizona Cardinals took advantage of a lot of 49ers mistakes for a 28-18 victory at Levi’s Stadium, giving first-year head coach Steve Wilks his first win.

It was the Cardinals' seventh consecutive victory over the 49ers, who fall to 1-4 on the season.

Here are three takeaways from Sunday’s game:

Lacking in passing game

49ers coach Kyle Shanahan schemed up the first drive of the game with a plethora of short passes to slow down the Cardinals’ blitzes. But after Arizona made the adjustment, the 49ers didn't have enough offensive firepower to create much of a threat.

Wide receiver Marquise Goodwin was inactive with hamstring and thigh issues. His backup, Dante Pettis, didn't suit up because of a knee injury. The 49ers were lacking speed on the outside, which is a requirement for Shanahan’s offense. Rookie Richie James made his first career start after being inactive for three of the first four games. He caught one pass for 7 yards.

Moreover, receiver Pierre Garçon sustained a shoulder injury in the first quarter. He returned before the end of the first half, but he was largely ineffective. Quarterback C.J. Beathard didn't get much help from Garçon, who had a deep in-route deflect off his hands for a first-quarter interception.

Beathard completed 34 of 54 passes for a career-high 349 yards with two TDs, and he also was picked off twice. He was sacked four times and lost two fumbles.

Secondary ups and downs

Veteran cornerback Richard Sherman was back in the 49ers' starting lineup after missing just 1½ games with a mid-calf strain. But it’s the play on the other side that is the team's much greater concern.

It didn't take Cardinals rookie quarterback Josh Rosen long to exploit the 49ers’ play at right cornerback.

On the opening play of Arizona’s first drive after the 49ers took a 6-0 lead, rookie wideout Christian Kirk beat cornerback Ahkello Witherspoon deep. Free safety Adrian Colbert, who was playing the deep middle, ran up and allowed the pass to sail over his head for a 75-yard touchdown.

Cornerback Greg Mabin rotated into the game with Witherspoon, while Sherman played the entire game on the other side.

After the first play, the 49ers’ defense played well enough to win, as the pass defense tightened up. Rosen completed just 10 of 25 passes for 170 yards and one TD. He didn't have a throw intercepted.

Help needed at running back

The 49ers have been preparing to add a running back in recent weeks, with Matt Breida and Alfred Morris experiencing some injury concerns. That time might be now.

Breida sustained a left ankle injury in the first quarter and didn't return. He underwent X-rays, which were negative, according to a source.

The 49ers are hopeful that Breida will be able to play next Monday night against the Green Bay Packers, and his presence was sorely missed in this game. He had 56 yards on eight carries before the injury.

Raheem Mostert entered the game after Breida’s injury and fumbled on his first rushing attempt. Patrick Peterson picked up the loose ball and returned it 49 yards to set up the Cardinals’ second touchdown.

Morris rushed for a game-high 61 yards on 18 rushing attempts.

The 49ers could look outside the organization or promote undrafted rookie Jeff Wilson from the practice squad.