LOS ANGELES — For the first 30 minutes of USC’s 41-28 win over Stanford on Saturday in Palo Alto, the Trojans looked better than they’ve looked in at least five years, maybe 10.

Heck, when USC was really rolling late in the first quarter, you could’ve compared them to a Pete Carroll Trojan squad, and you wouldn’t have been too off.

Caleb Williams was on fire. Jordan Addison looked like a seasoned professional. The defense was timely and opportunistic. Forget hitting on all cylinders. The entire engine was roaring.

But the Trojans came back down to earth in a surprisingly close second half — when they were outscored by Stanford, 14-6 — and USC came out of the game somewhat somber despite the big win.

First, Riley celebrated the rare win in Palo Alto, just USC’s second at Stanford since 2009.

“This series has been extremely one-sided over the last 15 years, especially here,” Riley said. “We took that personal. The two sides of you right now, I’m thrilled for the victory and that overshadows — not overshadows, it’s definitely the No. 1 thought and takeaway … look at 12 months ago. Look at 12 months ago. This is a good Stanford team, and a lot’s changed. I’m proud of the way our guys responded. Road victories in conference are like gold. I told y’all that beginning of the week, and that was a huge win for us.”

And yet, Riley added…

“We didn’t play very good — didn’t play up to our standard — offensively in the second half,” he said. “We had some good opportunities, had some good field position. … (but it) wasn’t very good by the team, wasn’t very good by me in the second half.”

So what does that means going forward for the Trojans?

A lot of certainty. And a lot of question marks.

Most of all, despite one of the best first quarters in their recent history, USC walked out of the game feeling the worst three letters in all of college football.

Meh.

*****

When USC sets a standard like it did in the first half against the Cardinal on Saturday, there’s going to be a letdown.

The Trojans picked off talented Stanford quarterback Tanner McKee on the first drive of the game. Then, after three straight runs put the ball at the 5-yard line, Williams found Lake McRee for the passing score. Stanford drove the ball to the 2-yard line on its next possession, but once again, USC’s defense rose to the occasion as Mekhi Blackmon picked off McKee for the second time.

Williams went 3-for-4 on the ensuing drive, capping it off with a 22-yard touchdown pass to Addison, and after the Cardinal scored on their next possession to get on the board, USC responded in a hurry with Williams hitting Addison on a 75-yard scoring strike to go up 21-7.

It was as good a first quarter as any in recent conference history.

And it only got worse for the Cardinal in the second quarter, with E.J. Smith fumbling at the 2-yard line on Stanford’s first drive of the quarter. Williams found former Oklahoma teammate Mario Williams on a pair of deep passes on the ensuing drive, one for 43 yards and the second a 15-yard scoring connection, and after Stanford scored once more to cut the lead to 28-14, Travis Dye ran it in from 27 yards out to give the Trojans a three-score lead once more.

It was USC’s fifth touchdown in five drives, and ninth score in 10 first-half drives in the first two weeks.

*****

For one play in the second half, the Trojans were still rolling.

After being denied a scoring opportunity on the final drive of the first half, Williams opened the second by connecting with Addison for a 48-yard completion.

To that point, Williams was dialed in.

And then the phone came off the hook.

Williams misfired on two straight passes as USC settled for its first field goal of the quarters. Another long USC drive stalled after a Williams incompletion and sack and the Trojans settled for a missed field goal. Then, after yet another E.J. Smith fumble at the Stanford 29-yard line, USC squandered terrific scoring opportunity and was forced to settle for yet another field goal, going up 41-14.

It would be USC’s last score of the game.

Stanford would add two more touchdowns to make it competitive, but late rally fizzled and the Trojans walked away with the victory.

By so many standards, it was a fine win.

But after that first quarter, it could’ve been so much more.

The good thing is, Riley realizes it.

“The good is really really good, on all three sides; the bad is not good enough right now,” he said. “That’s coaching, that’s offense, defense, special teams. There’s too much inconsistencies. For us, it’d be great to raise the ceiling of our play, but more than anything, we’ve got to take the bottom part of play — the not good plays — we’ve got to raise those up.”