Stanford’s defense has holes to fill, but can rely on...

There are two central questions for Stanford’s defense ahead of the 25th-ranked Cardinal’s season opener at home against Northwestern on Aug. 31:

1. How will Stanford make up for the loss of its top two tacklers from last season?

2. Just how good can cornerback Paulson Adebo become?

The Cardinal lost inside linebacker Bobby Okereke (team-high 96 tackles and a third-round pick of the Indianapolis Colts) to graduation and inside linebacker Sean Barton (92 tackles) gave up football with a year of eligibility left.

To help fill that void, 6-foot-3, 236-pound senior Curtis Robinson has switched from an outside linebacker to an inside ’backer.

Head coach David Shaw said Wednesday that during training camp, Robinson “has been just a blessing. He’s been so fast and physical. He’s gotten comfortable in there.”

Robinson and Jacob Mangum-Farrar, who played in the Cardinal’s final four games last season as a freshman, are the likely starters at inside linebacker. Ricky Miezan, who also played in the final four games of 2018 as a freshman, Andrew Pryts and Ryan Beecher are in the mix.

Outside linebacker Casey Toohill said trying to predict which two players will lead the Cardinal in tackling might rate as a wasted exercise.

“I don’t even really think we should single out guys,” said Toohill, a fifth-year senior. “I’m not too worried about” who the top tacklers will be. “You lose guys every year, right? There needs to be that opportunity for the next great guy to step in.”

Stanford does return the man who made the third-most tackles (64) last season. That would be Adebo, an Associated Press first-team preseason All-American who led the Cardinal with four interceptions and 20 pass breakups.

Safety Malik Antoine said Adebo is “one of the hardest workers I know. He’s really determined.”

Backing up Antoine’s point: Adebo was the last player off the field after Wednesday’s practice.

“I’m just trying to be better than I was last year,” said Adebo, who’s listed at 6-1, 190 pounds. “There are a lot of expectations; (I’m) just trying to meet ’em. … I think I have higher expectations (for myself) than anybody else has for me.”

Making Adebo’s 2018 performance even more impressive: It was his first season on the field. He had redshirted as a freshman in ’17.

“He’s got great instincts,” Shaw said of Adebo. “He’s got great feel for routes. He’s got great ball skills to both deflect passes and also try to intercept them. And he’ll come up and hit you.”

Said Toohill: “It’s just fun to watch, man. You see someone who’s just so good at (his) job. It’s not even a surprise when it’s an insane interception. … It’s just lock down every play.”

Briefly: Shaw said that though his assistant coaches have remained in training-camp mode this week, he has devoted some time to game-planning for the Cardinal’s first three opponents (Stanford is at USC in Week 2 and at No. 17 Central Florida in Week 3). “I kind of peek over the fence a little bit to see what’s coming,” Shaw said. … K.J. Costello enters his third season as Stanford’s starting quarterback. Northwestern hasn’t named its starting QB; Hunter Johnson, a transfer from Clemson, and T.J. Green, a fifth-year senior who’s the son of former NFL quarterback Trent Green, are the leading candidates. … This will be the Wildcats’ second straight game on the West Coast against a Pac-12 team. They beat Utah 31-20 in the Holiday Bowl in San Diego on New Year’s Eve.

Steve Kroner is a San Francisco Chronicle staff writer. Email: skroner@sfchronicle.com Twitter: @SteveKronerSF