SANTA CLARA — It shouldn’t be surprising that the 49ers are trailing at halftime on their home field, where they haven’t won since Oct. 18, 2020.

It’s stunning, however, how they’ve fallen behind 17-7 and against an Arizona Cardinals team missing Kyler Murray, DeAndre Hopkins, A.J. Green and J.J. Watt.

The 49ers defense has been doomed by missed tackles, poor pass coverage and, most galling, penalties on Arik Armstead and Josh Norman, the latter of which got the veteran cornerback benched.

The 49ers offense, meanwhile, saw George Kittle and Brandon Aiyuk each fumble after 18- and 22-yard receptions, respectively.

Here is a more detailed recap of the (expletive) show by the home team:

What kind of spark has George Kittle brought?

Well, Kittle’s first touchdown catch of the season came with 16 seconds until halftime, and it came after Jimmy Garoppolo motioned him to a spot in the end zone for a 6-yard completion.

Kittle’s last touchdown came the last time the 49ers won at home – that October 2020 game against the Los Angeles Rams.

Kittle has four catches for 57 yards.

After a three-game hiatus to help his calf recover, Kittle was the last 49er introduced pregame, he is one of their three captains at the coin toss (Arizona won it) and he promptly got two targets on the opening drive (19-yard catch, pass breakup).

Then came the next drive, and Kittle made an 18-yard reception over the middle, only to have the ball punched from his grasp by Byron Murphy Jr. for the 49ers’ first turnover in two games.

And how about Brandon Aiyuk’s encore?

Two snaps prior to Kittle’s touchdown, Aiyuk infused life into a last-minute drive by making a 16-yard catch at the Cardinals’ 8-yard – and holding onto the ball after enduring two hits.

Earlier, he made two great catches (11 yards, 22 yards) in a three-play span, only to lose a fumble at the 8-yard line. That was the 49ers’ second turnover after they had none last week in Chicago, where Aiyuk rehabilitated his image with an all-around excellent game.

What was Josh Norman thinking?

Cornerback Josh Norman got pulled from a second-quarter drive after quite the egregious penalties.

The 49ers’ K’Waun Williams had made a third-down stop, during which Cardinals coach Kliff Kingsbury went ballistic on the field shouting at the officials, who responded by calling an unsportsmanlike conduct penalty on him.

Then Norman sauntered over and taunted Kinsbury, resulting in a taunting penalty that was assessed first for a first-and-25 situation for the Cardinals, who eventually settled for a field goal and 17-0 lead with 4:02 before halftime.

Meanwhile, Norman got replaced by Dre Kirkpatrick; Norman took a seat on the bench with other defensive starters after the series.

What is wrong with the 49ers’ defense?

After allowing a 100-yard rusher in back-to-back games, the 49ers’ run defense is not faring better. James Conner put the Cardinals ahead when he bounced a 13-yard touchdown run outside, and cornerback Emmanuel Moseley feebly missed an open-field tackle on the edge.

Earlier on that scoring drive, the Cardinals converted a pair of third-down snaps – on runs.

Conner scored on a 1-yard plunge on the Cardinals’ next drive, giving him 10 touchdowns this season and making sure Arizona doesn’t miss starter Chase Edmunds, who injured an ankle on the first snap.

Speaking of missed tackles, another came on a third-down conversion catch, when Azeez Al-Shaair whiffed at James Conner. Al-Shaair came back later on the drive to break up a potential Zach Ertz catch (fumble?), but later yielded a 16-yard catch to Ertz. (Dre Greenlaw’s return could be coming next week, sending Al-Shaair to the strong-side linebacker, part-time role.)

How does Colt McCoy look in place of Cardinals quarterback Kyler Murray?

McCoy is 12-of-15 for 145 ayrds with a 106.9 passer rating. He was 8-of-11 for 74 yards as the Cardinals built a 14-0 lead through the first quarter. He threw (and failed) on a deep pass early, tried (and failed) to outrun pass rusher Arden Key, and ultimately found relative success with short, horizontal screen passes that tested the 49ers’ boundary defense.

Early in the second quarter, McCoy spotted Christian Kirk with a couple steps on Talanoa Hufanga, resulting in a 50-yard completion to the 41. Later on the drive, McCoy converted on a third-and-1 sneak, but he got sacked on the next snap by Arik Armstead, then K’Waun

How did Arik Armstead swing the momentum?

Arik Armstead celebrated what appeared a third-down sack that could swing the game’s momentum to the 49ers.

Instead, officials called a 15-yard penalty for Armstead grabbing McCoy’s “helmet opening.”

No play depicted the 49ers’ first-quarter blues than that one.

On the next play, Arizona ran a trick play, with wide receiver Christian Kirk completing a 34-yard pass to the 1 to Antoine Wesley, against safety Tavon Wilson’s coverage with 42 seconds left in the quarter.

Predictably, Conner scored his second touchdown on the ensuing snap for a 14-0 lead, on a field where the 49ers haven’t won since Oct. 18, 2020.

How are the 49es’ running backs being used?

Elijah Mitchell, sore ribs and all, has 35 yards on six carries.

He got the start and ran 9 yards on the first snap, breaking a tackle along the way. Then the 49ers stubbornly abandoned the run on the opening drive and attempted five passes before punting. Noticeably, JaMycal Hasty remained their suspect third-down back, but Markus Golden’s third-down sack of Garoppolo came through center Alex Mack and right guard Daniel Brunskill.

Mitchell broke a tackle on his second carry (to limit the damage on a 5-yard loss) and then got their fourth drive going with an 11-yard run to the left behind Trent Williams and Mack.

Jeff Wilson Jr., meanwhile, has yet to surface in his season debut, after just getting activated Saturday following his May knee surgery.

Who’s winning between a depleted Cardinals receiving corps vs. a depleted 49ers secondary?

Replacement free safety Tavon Wilson combined with cornerback Emmanuel Moseley to break up a deep pass on the Cardinals third snap.

But McCoy’s 50-yard connection to Kirk later in the first half summed up how vulnerable that defense is without Jimmie Ward (inactive; quadriceps) and Jaquiski Tartt (injured reserve; knee).

Injury updates:

— Right tackle Mike McGlinchey sustained a second-quarter knee injury, went to the locker room for evaluation and was replaced by veteran Tom Compton, rather than rookie Jaylon Moore.

— Nose tackle D.J. Jones got injured making a tackle on the opening play, but he returned on the next series.

— Cardinals running back Chase Edmonds left after that Jones tackle with an ankle injury.

Source: www.mercurynews.com