It seemed like the fun was over.

Cal had opened the season with upset wins over UNC and Ole Miss. But after two brutal losses on the road where the team simply looked out of sorts, it was time to shut down the party. The high-flying offense of No. 8 Washington State was coming to Memorial Stadium, and it looked to be the closing act.

Cougars quarterback Luke Falk had parlayed years of tormenting Pac-12 defenses into a Heisman campaign that was peaking as he looked to carve up Cal’s defense. With only two interceptions on the season, the Bears’ turnover-dependent approach looked to be closing in on a brick wall. That wall tore like tissue paper.

On the third play of the game, Falk made a lazy throw across his body and was picked off by freshman cornerback Camryn Bynum. It was no fluke — Falk was beyond flummoxed, and a nightmarish spiral was under way. Before the night was over, his interception total had more than tripled, and Cal walked away with an absurd 37-3 win in which the betting line had them as two-touchdown underdogs.

It became something of a national coming-out party for Cal’s rapidly improving defense. But defensive coordinator Tim DeRuyter, responsible for three hours of priceless sideline glares from Wazzu offensive mastermind coach Mike Leach, knew it was just one more stop on his rehabilitation plan for the Bears. For a team that’s second in the nation in takeaways after years of 50-point shootouts, it’s fair to say that he and head coach Justin Wilcox’s patient is coming along pretty nicely.

The first thing that hits you is that there’s no way DeRuyter is really a Los Angeles native. He’s got the gruff voice and tough skin that you can order from “hardass football coach” central casting.

“A lot of people think I have a Southern accent, which I don’t think I do,” DeRuyter said. “It’s maybe more coach speak that comes out, but having worked in Texas and guys who were from the South, sometimes that rubs off on you.”

But it’s true. His father came to the United States from Holland and married an LA girl, and DeRuyter grew up in Long Beach. He attended St. John Bosco High School and was the sort of infuriating overachiever who managed to pull off football and school, taking recruiting trips to Harvard and Princeton. When all was said and done, he ended up at the Air Force Academy.

“I was looking to go to a school that had real high academics, and real good football,” DeRuyter said. “I tested out fairly good — grade-wise, I was one of the top in my class. … I wanted to play Division 1 football, so I was given a great opportunity academically, but you also get a chance to play against Notre Dame and BYU and some of those folks — that pretty much tipped the scales for me.”

DeRuyter was there for some of the golden years of Air Force football, racking up wins, bowl appearances and even a finish in the national top 15 in 1983. But as is the case with all coaches, the most important part of his time there was the connections that would put him in contact with some of the greatest minds in football history.

After an assistant coaching stint with his alma mater, DeRuyter briefly went into medical sales, moving to Pittsburgh. Also in Pittsburgh? Perhaps the most famous defensive architect in modern football history, Dick LeBeau.

It’s hard to explain just how much of a mystique LeBeau holds in the football world: He was only ever a head coach for a brief unsuccessful time with the Cincinnati Bengals, but he still may be the most vaunted and celebrated football mind of the last 30 years.

The only question was who would make the introduction. And luckily, DeRuyter had that figured out. His college position coach — and a future NFL head coach — Chan Gailey was with the Steelers on the opposite side of the ball.

“So (Gailey) called me and said, ‘Hey Tim, I’m just moving,’ ” DeRuyter said. “So Carol, my wife, and I had him over to our house for dinner and a welcome to Pittsburgh thing. … The Steelers have traditionally had great defense, so I called (Gailey) up and said, ‘Hey Coach, do you mind introducing me to Coach LeBeau. I’d love to find out what the Steelers are doing with their 3-4.’

The legend was a willing teacher.

“He welcomed us with open arms, and every year during the off-season, our staff would go and study what they did and incorporate some of the similar philosophies.”

With the best (occasional) mentor one could ask for, DeRuyter was let loose on schools hungry for defense.

Soon after began the whiplash portion of a coach’s career, careening from town to town. Ohio to Navy, back to Ohio, to Nevada, back to Air Force (this time as a defensive coordinator), and then to Texas A&M in the same role in 2010.

That’s when DeRuyter’s specialty started to come into focus. On top of having to integrate his 3-4 scheme (a change in base formation and personnel assignments), he had to overhaul the focus of a program. After being a strong defensive team in the 1990s, the Aggies had fallen apart and couldn’t stop a fly by the time DeRuyter arrived.

When things get to that point, a scheme switch isn’t enough. As DeRuyter learned and would end up certainly needing to know for when he came to Cal, years of bad defense leave a lasting mental effect that has to be undone.

“One, you better be around really good people and good leadership,” DeRuyter said. “Everywhere I’ve gone we’ve had that at the head coaching spot, guys that believe in team defense and defense being part of the big picture. … And then from my perspective as the coordinator, I try to get guys to see themselves differently from what they’ve been typecast as.”

The transition was as close to overnight as football gets. Texas A&M jumped from bottom five to above average in total defense and top 40 in defensive takeaways — a DeRuyter focus. It only took two years for another team in need of defensive overhaul to give DeRuyter his biggest shot yet, the head gig at Fresno State.

The Bulldogs were also coming off a dismal defensive year, but after DeRuyter’s first year? A top-25 defense. A combined 20-6 record over his first two years with Mountain West division championships didn’t hurt matters anyway. If you needed a turnaround, you knew who to call.

But things started to fall apart in Fresno after his first two years — a 6-8 record slipped to 3-9, and a 1-7 start to the 2016 season ultimately led to DeRuyter’s firing. A strange school swap soon began when former Cal coach Jeff Tedford took over with the Bulldogs, Cal fired Sonny Dykes far after most coaching hires were done, and Justin Wilcox — another 3-4 adherent — was brought to Berkeley. DeRuyter and Wilcox had mutual football friends all over the country, and they had been meaning to talk, so DeRuyter wasn’t shy about reaching out.

“I kept hitting him up every couple of days — ‘Hey, not sure where you’re at but I’m out here and ready to go,’ ”  DeRuyter said. “He eventually called me and we sat down and realized, ‘Hey, I think this thing could work.’”

Wilcox was working on a brief timeline with his late hiring, but it didn’t take long for him to realize there was a match.

“During that time, you can imagine, it’s pretty busy, so we finally got a chance to talk and come over,” Wilcox said. “I knew a lot of people who knew him, and they all said the same thing. He’s a great guy, a really good coach, and that we would get along fantastically, and that’s true. … Just his personality and his ability to communicate with people and connect people and get them on the same page has been huge for us.”

DeRuyter plays a particularly funny role on the coaching staff. Although they don’t lack for experience, Wilcox and offensive coordinator Beau Baldwin are just 40 and 45. Defensive backs coach Gerald Alexander sits at 33, and wide receivers coach Nicholas Edwards, 27, is easily mistaken for a player. DeRuyter is middle-aged at worst in the grand scheme of football, but on this staff, he’s somehow become the grizzled veteran.

“Whether you’re old or not, there’s got to be a feeling from the players that you’re in it for them,” DeRuyter said. “That you’re going to give them tools that will not only maximize their football ability, but in a bigger way maximize who they are as a person. … I think when you have experience like (I) do, they look at you a bit more fatherly, while guys like (Alexander) and (linebackers) coach Tony Tuioti as older brothers.”

It’s almost impossible to overemphasize the shift in defensive culture from the Dykes era to what Wilcox and DeRuyter have done so far. Not every defensive statistic is pretty, but in Cal’s biggest games, the defense has clamped down in a way that was unimaginable not long ago.

“What you want to do in my mind is set a brand and standard of football you want to play at,” DeRuyter said. “On defense, we talk all the time about taking the ball away, playing with fanatical effort. When you do that you got a chance to be a decent defense.”

Watch any second-half defensive eruption, or just come around to practice. You can see the players buying into the larger vision.

“I think across the nation you can tell the defense here at Cal is changing, it’s been a paradigm shift,” said linebacker Jordan Kunaszyk. “Since day one, the coaches have done a tremendous job at establishing a hard-nosed defense here.”

DeRuyter is still far from where he and Wilcox want to be. The late coaching change means half the defense is playing out of positions and learning new roles. During Cal’s worst moments, it’s extremely apparent.

But look at it this way. The life-saving surgery is done, and the Bears defense is on to physical therapy. A few wobbles here and there are far from the point. There’s a new focus in Berkeley, and it’s taken hold faster than anyone but DeRuyter could have imagined.