As the waning moments of Alemany High’s thunderous season-opening 43-0 victory against visiting San Fernando High on Aug. 17 vanished into the warm Southland evening, Warriors Coach Casey Clausen could relax and smile.

First games are tough enough when you’re a new coach with a new staff teaching a new system to a new team, where many of the players are playing in their first varsity game. Add a few degrees of difficulty to that when you, the coach, were a top player of the team back in the day.

“It was exciting to be back here,” said Clausen, who came to Alemany in December after spending the last four years as head coach at Calabasas High. “The kids had put in a lot of time and effort since January, when we got hired. But Game One, you never really know what’s going to happen. This year, as young and inexperienced as we are as a group, overall we were pretty pleased with how the kids competed.”

The optics on Friday were important to an Alemany home crowd whose attendance had noticeably thinned sometimes in the past two 3-7 seasons, which led to the hiring of Clausen in place of James Washington as head coach. And the crowd certainly liked what it saw on Aug. 17 — an uptempo style that riddled the Tigers with a passing offense that could overcome its own missteps, and a defense that bottled up San Fernando, not allowing any advancement past the Warriors’ 31-yard line. Afterward, the hugs and backslaps from fans given to Clausen and his coaches — which includes his brother Rick Clausen — were hearty and voluminous.

Of course, it was one game. This week’s nonleague road contest against Charter Oak (0-1) on Aug. 24 might be more revealing. Charter Oak went undefeated last season until losing in the section Division III playoff semifinals to eventual champion Rancho Verde High of Moreno Valley, to finish 12-1.

And if not, there will certainly be other tests along the way.

Which is why, Clausen said, he was not fooled by the apparent lopsidedness of the result. It did not signal to him that the Warriors (1-0) had been vastly underrated regarding their skillsets.

“I like this group, and it’s a very talented group. But we’re young, we’re green, we’re raw,” Clausen said. “For us, coming to the program from where we were, we kind of knew what to expect.

“Now four years ago, we were laying the the foundation, pouring the cement, and building the house [at Calabasas]. That’s where we are now over here — we’re laying the foundation and pouring the cement. [But] we’re not going to wait two years when everything is ready to go. We’re going to push them, and see how quickly we can upgrade and improve as a team overall.”

Clausen certainly has cachet at Alemany. As previously mentioned, he is an alumnus (Class of 2000) who played quarterback. He was also a college quarterback at the University of Tennessee and played pro ball in the NFL Europe league.

Washington had a resume, too, having played at UCLA and then in the NFL as a defensive back, where he won a Super Bowl with the Dallas Cowboys. But Clausen had something Washington lacked — high school coaching success. He won Southern Section titles at Calabasas in 2015 and 2016. It also didn’t help Washington’s cause when the man he replaced, Dean Harrington, has won Southern Section championships and a state title at Paraclete High.

Offensive lineman Dohnovan West, a senior with a handful of scholarship offers, said he had considered transferring when Washington resigned. Whoever was coming would have been his third head coach in four years. And quite a few players he knew from last season had already left the program or graduated.

But West decided to stay and — for at least one game — was encouraged by what he saw in the San Fernando game.

“For me, it was more important to get through the first game and see how things go,” West said. “Our team’s really young — I think we only had four guys who had played in a varsity game prior to Friday. So it was important to see what the young kids could do. And they did pretty well.”

And his early impression of Clausen and staff?

“It’s kinda cool to see someone who came here and walked in those shoes come back and give back to the program. They’ve brought a new style of offense compared to what I played last year. Learning the new techniques was helpful; it adds more to my skillset.”

On the other end of the spectrum was sophomore quarterback Miller Moss, making his first ever varsity start. He had an excellent game, throwing for 241 yards and a pair of touchdowns. It could have been better but his receivers dropped several passes, and other drives were curtailed by penalties.

“I think that being successful that first game can set a great precedent for the rest of the season,” Miller said. “There was [still] a lot to learn from that game. I feel we executed pretty good. But certain things, because we’re young…most of our errors were because of youth. That will improve over time.”

Clausen couldn’t have said it better himself. And he probably did say something like that after playing games here.

Alemany was moved from Division I to Division II this season, but still resides in the highly competitive Mission League and has missed the playoffs the last four years. Alumni (and administrations) can be notoriously impatient with “program building” no matter how much they may like the coach.

So will Clausen have the chance to keep “laying the foundation” and “pouring the cement”? Does the house get built? Or only half-built?

“I think everyone, if they’re realistic, knows what we walked into. If they know us, they know what we left and know what’s here — I think that’s why we’re here,” Clausen said. “We’re here to build something that not only the school but community can be proud of. The administration wants this to be a premiere football program. That doesn’t happen overnight. But we know the resources, and of the commitment from the school and administration.

“That’s why we’re here. We’re here to grow that, develop that, build that, and mature that as quickly as we can. Again, what does that mean this year in wins and losses? I don’t know. But I’m pleased with the group we have.”