SAN FRANCISCO — The shutout was important to Isaac Sopoaga. The phone call was vital. The call arrived Saturday afternoon, roughly 24 hours before the former University of Hawaii star put on his 49ers uniform to play the St. Louis Rams.

All week long, Sopoaga had been waiting for word from his family in American Samoa. Tuesday morning, a tsunami had slammed the island nation. Sopoaga’s village of Fagasa is an isolated fishing community. Communications were down.
“I was worried,” Sopoaga said. “Not sad. Not scared. Worried. Worried.”
Finally, while Sopoaga was at the 49ers’ walk-through practice Saturday, his mother reached his wife. Everyone was safe.
“They’re good,” Sopoaga said Sunday. “The water stopped, like, 15 yards from their house. It hit one building where my cousins worked, but they escaped. The water didn’t touch them.”
Worried no more, Sopoaga celebrated by doing what he does best. He lined up at defensive end Sunday and — with his teammates — made the St. Louis Rams’ lives completely miserable.
How miserable? In the 35-0 rout, St. Louis’ offense never made it inside the 49ers’ 20-yard line.
In other words, the tsunami surge came closer to the Sopoaga home in Fagasa than the Rams’ offense ever came to the goal line at Candlestick Park.
And, no, Sopoaga did not mind the somewhat flip analogy.
“I feel great about today,” Sopoaga said. “We got to do what we do. We were out there having fun.”
In this young 49ers season that has provided several unexpected story lines, Sunday actually was one of the more predictable outcomes. The winless Rams are a very bad football team. But the 49ers made sure the Rams stayed very bad, from start to finish.
Sopoaga and his defensive colleagues deserved most of the credit. As the 49ers’ offense continued to search for an elusive groove, their defense held the Rams to 177 net offensive yards and nine first downs — resulting in the first 49ers shutout victory since the 2001 season.
“A shutout is the ultimate for any defense,” said linebacker Manny Lawson.
“Once we got to the fourth quarter,” said lineman Ray McDonald, “we needed to get a goose egg and show everybody we were for real.”
McDonald helped cement that real-ness by picking up a fumble and scoring a touchdown. But to show you what kind of game it was, that play didn’t even qualify as the day’s best defensive highlight.
Nope. That one belonged to linebacker Patrick Willis, who snatched an interception and sprinted 23 yards for another six points. Also, as usual, Willis continued to tackle every moving object in his field of vision. For the 49ers, this strategy seems to be working well.
Willis wasn’t truly everywhere, of course. It just seemed that way. Over and over, Willis hauled down steamroller St. Louis running back Steven Jackson. Three times, Willis reached quarterback Kyle Boller behind the line of scrimmage and sacked him. Then came the pick-six capper.
“Today was one of the better games that I have had since I’ve been in the league,” Willis said. “But it wasn’t just me. It was our defense altogether. “... It was just a day where you just say, ’Wow.’ “
That “wow” factor began in the trenches with Sopoaga and McDonald, then spread back through the linebackers and the safeties.
As you might expect, this still wasn’t “wow” enough for coach Mike Singletary.
“Don’t misunderstand me,” Singletary said. “I’m excited about our defense. But because I know them and know what they’re capable of, I just don’t want our guys to go, ’Hey, we’re there.’ We’re going in the right direction. But there’s so much more that we can do.”
Imagine, then, what Singletary must think of the offense. Clearly, running back Frank Gore is missed. However, quarterback Shaun Hill keeps managing the ball safely enough. He had no interceptions Sunday and threw for two touchdowns. And he was properly grateful for his defensive teammates.
“I love watching them play,” Hill said.
For now, at least, the 49ers have indeed found a formula that works. Namely: If the defense plays relentlessly wicked football, the offense can give them just enough oomph to win. It’s why they are 3-1 for the first time since 2002, their last winning season.
Sopoaga, a quiet man, probably exemplifies the 49ers’ team mojo as much as anyone. He is serious about building a new reputation for the team. Serious enough that he could compartmentalize his concerns for his family in Samoa and concentrate on the game plan.
“Isaac is a high-spirited guy,” said McDonald. “He’s not too big on bringing his personal life into his football. But we want to support him any way we can.”
Sunday, they supported him by supporting each other and slamming the Rams. It’s why Sopoaga could leave the locker room with a smile on his face. For many reasons.