USC’s Sam Darnold is having passes intercepted more often this season. Why?

USC’s Sam Darnold uttered some words of regret on Sunday as he and quarterbacks coach Tyson Helton watched what usually should’ve been another addition to Darnold’s highlight reel.

Against California the previous day, Darnold saw pressure at the last minute, ducked out of the way and made a long throw to the corner of the end zone while on the run just before absorbing contact. The ball lofted past the deep safety. Deontay Burnett ran for it. He dived.

And — he missed it. The throw was too far.

In the film room, according to Helton, Darnold said, “Man!” and added that he should’ve had the touchdown.

“You look at Sam and you see that and you say he’s hit that so many times, the one time he doesn’t, ‘What’s wrong?’ ” Helton said a day later after practice. “And with a normal person, I still don’t know if they make that throw.”

Helton smiled and shrugged. “Sometimes you hit ‘em, sometimes you don’t,” he said.

Darnold made accurate throws like that so consistently last season that he is now graded on his own, different curve. By those standards, Darnold has experienced a drop-off in two significant areas in this season’s four games: touchdowns (nine) and interceptions (seven).

Most of Darnold’s peripheral stats still sparkle. His percentage rate, 67.1%, is a single completion behind last season’s rate as a starter. Last season, he threw for 295 yards a game as a starter. This season he’s up to 306 yards and has yet to encounter the cupcake secondaries that populate much of the conference.

Still, he had just nine passes intercepted all of last season, and now he’s nearly got that many in four games. What’s going on?

The answer matters a great deal to USC’s national title aspirations and, more pressingly, to its crucial Friday night game at Washington State. The Cougars score lots of points behind Luke Falk, their own star quarterback. USC needs Darnold to be at his full, dynamic potential.

Yogi Roth knows Darnold well and recently reviewed tape on each of Darnold’s seven interceptions. Roth, a Pac-12 Networks analyst who hosts a weekly podcast with Darnold, concluded the quarterback made some bad throws or decisions. But Roth did not find any consistent bad habits.

“Picks are picks, and you can’t turn it over,” Roth said. “That’s your No. 1 job as a quarterback, I think, is to protect the ball. But to me it’s not a cause for alarm, like, ‘Oh my god, he’s not seeing the field.’ ”

Roth then went through each interception. Two weren’t really Darnold’s fault: One was a receiver’s drop and another a receiver’s losing a one-on-one battle.

One was a mistake endemic to most college quarterbacks: losing track of the weakside linebacker. One, against Texas, was an airmailed pass to a wide-open tight end, like a Clayton Kershaw wild pitch.

The remaining three were of greater interest to USC moving forward. It’s when Darnold’s bravado can get him in trouble.

Two came against Stanford and one against Cal. Darnold saw a flicker of space, tried to squeeze those passes into a tight windows and missed.

Internally, there is disagreement over how to view such attempts.

“I think that’s me just trying to force things,” Darnold said.

“There’s gonna be so many times he makes a great play where you go, ‘Wow, that’s a great play,’ ” Tyson Helton said. “Every now and then, he’s gonna have a forced throw.”

“Literally I can count on one hand, there’s been really like two forced throws in my mind,” head coach Clay Helton said.

Either way, both Heltons have made their peace with those throws. The allure of Darnold is that he is willing and able to make throws that almost no other quarterback can. “So you gotta take the good with the bad,” Tyson Helton said.

The uptick in interceptions is better explained by defensive adjustments. Darnold thrived against the blitz as a freshman. According to Pro Football Focus, his 101.0 passer rating when pressured was No. 6 in the nation.

This season, Tyson Helton said, teams have mixed up their blitzes, disguising them better. On third down, teams rush less often. Instead, they have eight defenders in pass coverage. If defenses can’t stop Darnold from improvising, they try to limit his options when he does.

At times, the different array of coverages have goaded Darnold into bad decisions. Two of his throws early against Cal might have been worse than his one actual intercepted pass. And defenses have limited his deep passes. In Pro Football Focus’s rankings of the top eight quarterback prospects, Darnold comes in last this season on deep ball rating.

Offensive coordinator Tee Martin also explained that Darnold trusts his receivers to make plays. And this season’s group is less skilled than a season ago, and it was further depleted by an injury to Steven Mitchell Jr.

“I think I’m just getting impatient,” Darnold said.

Darnold has experienced no drop-off in one area of the game: the fourth quarter. He has three touchdowns, one interception and 287 yards in the fourth quarter or overtime this season.

At times, coaches have sounded weary answering questions about whether something is wrong with Darnold when he has yet to lose a game this season.

“I think right now he’s 13-1 as a starting quarterback,” Clay Helton said. “And that’s the No. 1 thing when you’re talking about quarterbacks. Do you produce for your team and do you produce wins for your team? And he’s as good as they get at it.”

zach.helfand@latimes.com

Follow Zach Helfand on Twitter @zhelfand