There were some positive early signs for Stanford on Thursday night. For one, Reid Travis was in the lineup after missing two games with a shoulder injury. For another, the Cardinal were hitting practically everything they shot.

They jumped to a quick 20-point lead and rolled to an 84-54 rout of Washington State. It was not only their first Pac-12 win after four defeats and their first under head coach Jerod Haase, but it was also their most one-sided win of the season.

They had played against the Pac-12’s elite teams and paid the price for it. They didn’t forget about the 39-point loss to Arizona, the 16-point loss to USC and the 14-point loss to UCLA. They just learned painful lessons.

“It was never that we were holding our breath for our first win,” point guard Robert Cartwright said. “That’s never how we looked at it. After every loss, we learned from it.”

Travis, their leading scorer and rebounder, returned to the lineup much sooner than expected after missing two games with a shoulder injury. He didn’t look hampered at all, producing 17 points and six rebounds.

“I feel great,” he said. “I don’t think they would have put me out there if I wasn’t 100 percent.”

But the big story for Stanford (9-8, 1-4 Pac-12) was Cartwright. Given just his fourth start of the season on the strength of his 18-point, nine-assist performance against UCLA on Sunday, the sophomore point guard poured in a career-high 21 points, hitting 5 of 7 three-point tries. He also passed out seven assists.

“I was surprised by the score, but I’m not surprised that we’re making progress,” Haase said.

As Cartwright saw it, their defense is what helped Stanford jump to a 25-5 lead and then hold a 48-23 lead at halftime. In Cardinal parlance, a “turkey” is three defensive stops in a row. “We had seven (turkeys) in the first half,” he said. “When we’re able to play defense like that and lock in, we’re going to be able to compete in a lot games and beat teams.”

Stanford held Josh Hawkinson in check with a double-teaming defense until the outcome was decided. He had 14 points and eight rebounds. Stanford limited the Cougars (9-7, 2-2) to 32 percent shooting from the field. On offense, the Cardinal did practically whatever they wanted.

The Cardinal entered the game as the Pac-12’s worst shooting team (43 percent) and worst three-point-shooting team (30 percent). Against the Cougars, they hit 55 percent overall and 56 percent on threes.

Dorian Pickens added 18 points and Marcus Sheffield 10 for the Cardinal, who committed just nine turnovers and enjoyed a 43-25 rebounding advantage. Michael Humphrey grabbed a game-high 10 rebounds.

“I thought they just physically manhandled us,” WSU head coach Ernie Kent said.

Conor Clifford led the Cougars with 15 points. Ike Iroegbu had 13 and Robert Franks 10.

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