Reality has set in for Stanford. It can’t run the ball — with Bryce Love or, as was the case Saturday night against Utah, without him.

It wasn’t the only reason the No. 14 Cardinal were upset 40-21, but it is a continuing and frustrating pattern. They had just 42 yards rushing, while the Utes had 222.

The loss ended Stanford’s 11-game home winning streak and dealt the Cardinal (4-2, 2-1 Pac-12) a severe blow to their hopes of repeating as North Division champions.

“It’s up to me to make sure this football team is playing our best football,” head coach David Shaw said. “Usually by now (midseason) we are, and we are not.”

Stanford wore black uniforms Saturday night. Previously, it had won eight out of nine times wearing black. This time the color reflected the Cardinal’s mood afterward.

Zack Moss rushed for 160 yards and two touchdowns, Jaylon Johnson had a 100-yard interception return for a touchdown, and Matt Gay kicked four field goals as the Utes remained unbeaten in four appearances at Stanford Stadium. Quarterback Tyler Huntley connected on 17 of 21 passes for 199 yards.

His most significant pass came midway through the fourth quarter when, after shaking off linebacker Gabe Reid in the backfield, he launched a 57-yard touchdown pass to Samson Nacua. Huntley has had an up and down year; in fact, it was his first scoring pass in 16 quarters. It put the Utes up 37-21, and they were on their way.

Stanford schedule Date Opponent Time/ Result Aug. 31 San Diego St.W, 31-10 Sept.8 USC W, 17-3 Sept. 15 UC Davis W, 30-10 Sept. 22 at OregonW, 38-31 Sept. 29 at N. DameL, 38-17 Oct. 6 Utah L, 40-21 Oct. 18-y at Arizona St.6 p.m. Oct. 27 Washington St.TBD Nov. 3 at Wash. TBD Nov. 10 Oregon St. TBD Nov. 17 at Cal TBD Nov. 24 at UCLA TBD y - Thursday

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“Not a lot of guys can make that throw,” Shaw said.

On the other hand, Stanford’s K.J. Costello committed three turnovers, most critically a couple of red-zone interceptions in the second quarter.

Trying to hit JJ Arcega-Whiteside in the end zone, he underthrew the ball, allowing Johnson to pick it off and go the distance for a touchdown. On the next series, Costello tried to get a pass off as he was being sacked. It went directly to tackle Huati Pututau, and it led to another touchdown that gave the Utes a shocking 21-0 lead.

“Those two plays were rough; I know he’d love to have them back,” Shaw said of Costello. “He’s still growing and learning. He’s not there yet.”

Costello was plainly upset with himself. “We pride ourselves in protecting the football, most importantly in the end zone,” he said.

Shaw said he realized Saturday morning Love wouldn’t be able to play. “If we played in a couple more days, he probably would have been ready to go,” he said.

He said the left ankle injury that Love sustained at Notre Dame is “not a long-term thing.” He said he expected that Love would be “raring to go” against Arizona State on Oct. 18 following a bye week.

Redshirt sophomore Trevor Speights had 56 yards in 17 carries, including a touchdown, in his first collegiate start.

Tight end Kaden Smith said, “I wouldn’t put (Love’s absence) on us as the reason we lost.”

One thing is clear: No matter how anemic the running game is, don’t expect Stanford to open up an Air Shaw type of passing attack.

“Some people will write that we should change what we do, that we should just throw the ball all over the yard,” Shaw said. “Those people don’t know me. Those people don’t understand this program. Those people don’t understand what it’s taken to get where we are and how many games we’ve won in the philosophy that we have. It’s a proven philosophy if we will execute.”

With Stanford falling behind 21-0, 27-7 and 37-21, Costello had to pass. He did so for 381 yards, completing 26 for 41 passes. He dropped a 26-yard touchdown pass on freshman Michael Wilson, giving Stanford a fleeting glimmer of hope late in the third quarter.

“We don’t want to be dropping K.J. back 60 times a game and make him vulnerable to more big hits,” Smith said. “So we really need to get this run game going and open up more holes.”

Smith had a career-high 120 yards on eight catches, while two other receivers also reached 100 yards. Arcega-Whiteside caught eight for 103 and Trent Irwin seven for 100. It wasn’t enough.

Briefly: Stanford safety Frank Buncom was initially called for targeting after a big hit on wide receiver Siaosi Mariner, but the penalty was overturned after a replay review. … It was Stanford’s worst home loss since a 42-16 defeat to Washington State in 2016. … Linebacker Bobby Okereke led Stanford with a career-high 12 tackles.

Tom FitzGerald is a San Francisco Chronicle staff writer. Email: tfitzgerald@sfchronicle.com Twitter: @tomgfitzgerald