Sam Darnold struggles, and so does No. 5 USC in loss to No. 16 Washington State 30-27

Sam Darnold trotted onto the field with 1 minute and 40 seconds left in USC’s 30-27 loss to Washington State on Friday night, a situation Darnold relishes and that USC has come to increasingly, and dangerously, rely on.

The Trojans trailed by three. Playoff implications for two teams hung in the balance. And no one on USC had many doubts.

“I thought it was automatic points,” said safety Chris Hawkins, watching from the sideline.

“We were excited,” quarterbacks coach Tyson Helton said. In the coaches box above the field, “Everybody’s like, ‘Here we go.’ We were pumped up.”

And on the field, Darnold pushed his thumb into his chinstrap buckle, plucked his mouthpiece from his facemask and settled into shotgun formation. He, too, believed USC would win the game, maybe with more conviction than anyone.

“Always,” Darnold said.

Always had lasted one year and six days, the span since USC’s last loss, in Darnold’s first career start. In between, Darnold had consistently pulled rabbits out of hats, as he did against Washington last season, Penn State in the Rose Bowl and Texas earlier this season.

But there was no magic on the Palouse. Darnold sat in the pocket and found no one on the first play. On the second, Jahad Woods raced through the middle of the line untouched. Darnold tried to heave a pass away. The ball squirted out and Derek Moore fell on the fumble.

Darnold put his hands on his hips and jogged to the sideline. The 33,773 fans at Martin Stadium had to wait another 1:26 before jumping, stumbling and dancing onto the field.

“It’s like Woodstock, except everybody’s got their clothes on,” Washington State coach Mike Leach said.

Darnold and his teammates weaved through the wave to reach a despondent locker room.

“I cried, honestly,” Hawkins said.

“It’s been a while since we felt like this,” coach Clay Helton said. “And it hurts.”

Darnold had endured perhaps the worst start of an otherwise spotless career. He connected on 52% of his passes (15 of 29), his worst completion percentage at USC. He threw for only 164 yards, his lowest total. He rushed for two scores but threw for none and had one pass intercepted.

“I didn’t play my best, for sure,” Darnold said.

His receivers — without starters Jalen Greene, who did not play in the second half, and Steven Mitchell Jr., who missed the game because of a groin injury — were smothered. Darnold clutched more than a kid learning to drive. When he did pass, his throws were sometimes errant.

Offensive coordinator Tee Martin cautioned he would know more after watching film, but said, “We just didn’t do good enough to consistently make the plays.”

Asked whether USC’s receivers got open, Martin said, “Yeah.” Asked why it was difficult to settle into an offensive rhythm against Washington State, he said, “They’re good.” Asked about his own play calling, he said, “We didn’t win a game.”

He continued: “The ultimate goal is to win. So if we don’t win, then it wasn’t good enough.”

Friday’s game was no offensive clinic. A clash of two high-flying offenses devolved into a muddy fight in the second half. And there was plenty of slop to go around: From USC’s entire offense, to the hands of Washington State’s receivers, to one USC play call — at last USC’s first quarterback sneak this season — when the Trojans were unaware they had already gained a first down.

Washington State outgained USC 462 yards to 327. Without three starting linemen, USC rushed for 163 yards in 29 carries, although 86 of those came on one Ronald Jones II rush.

USC’s defense neutralized Washington State for long stretches and at times in the second half made the Cougars look ugly. But the Trojans yielded too many long, back-breaking third-down conversions.

Washington State converted on three third-and-10 plays and one when facing third and 14.

“We have to get off the field,” Cam Smith said. “And there were some times when we didn’t.”

USC took a 17-10 lead in the first half behind touchdown runs from Darnold and Jones, who finished with 128 yards and a touchdown in 14 carries. Stephen Carr carried five times for 11 yards before leaving because of a lower-body injury.

But it was Washington State that struck at the end of each half. It was the Cougars who mounted a 12-play, 94-yard scoring drive, capped by a one-yard Jamal Morrow run, to tie the score with 17 seconds left before halftime.

It was the Cougars who used a shovel pass to Morrow for a 23-yard touchdown pass to break the stalemate and give Washington State a 27-20 lead in the fourth quarter.

Darnold and USC showed a brief outburst after Washington State’s score. On fourth and 13 in the fourth quarter, Darnold heaved a pass into coverage and somehow connected with Tyler Vaughns for 15 yards. He hit Vaughns again for 26 more to the one-yard line, then ran it himself to tie the score late. Vaughns led USC with six catches for 89 yards.

But it was the Cougars, again, who responded by driving down the field in the final minutes to kick the game-winning field goal, a 32-yarder by Erik Powell.

Luke Falk, Washington State’s own outstanding passer, completed 34 of 51 attempts for two touchdowns with one interception. USC sacked him five times.

Morrow rushed six times for 91 yards and caught six passes for 55 yards.

The Trojans still had ample chances to win. Instead, they doomed themselves with the same mistakes that had nearly cost them in their previous four games: penalties (nine for 80 yards), third-down inefficiency (two of 11) and the inability to finish drives with touchdowns.

“That’s a good team we played, but I don’t think we really played to our full potential,” Hawkins said.

If one sequence could encapsulate a game, it came in the second quarter:

USC’s Uchenna Nwosu had intercepted a Falk pass on a circus play. While blitzing, he’d swatted the ball, knocking it into the facemask of a Washington State lineman, then lunged to catch the carom. The interception set up the Trojans on Washington State’s three-yard line.

USC ran a dive. Nothing. Then USC called a quick pass to freshman tight end Josh Falo, who had yet to make a reception in college. He was covered. Nothing.

Then another dive.

Nothing again.

zach.helfand@latimes.com

Follow Zach Helfand on Twitter @zhelfand