The Giants multitudes hardly ever grumble about the home team inside happy fun joy-joy stadium, officially known as AT&T Park.
I think there's a rule about it or something. Do you have to swear a loyalty oath before buying a ticket and donning a Panda Hat?
Except ... on Sunday, a distinctive nonfestive noise carried through the ballpark when manager Bruce Bochy summoned Santiago Casilla with one out in the ninth and the Giants nursing a 3-2 lead over the downtrodden Houston Astros.
It was unmistakable and positively Candlestick-ian: Hundreds or maybe thousands of the Giants faithful were expressing loud displeasure with Casilla's shaky recent efforts and with Bochy's decision to put him back out there.
The boos didn't seem to register with Casilla, who took the mound with a stern and steady look and then recorded the final two outs easily for his 23rd save.
The fans cheered, of course, and the players celebrated on the field -- another Matt Cain victory, another leg up on the Dodgers in the National League West race.
But I think the ninth-inning boos were also part of a larger phenomenon: Giants fans were realizing that Casilla is the closer, is Bochy's guy, and will be the closer for now and probably for as long as the season goes.
And they weren't about to forever hold their peace about it.
"He's done a great job," Bochy said of Casilla when asked if getting that save after that reception was an important moment for Casilla.
"You're going to have hiccups. (Brian) Wilson did at times. (Casilla) had the finger (blister) going on, I think that affected him. Last night, he gets a strikeout to end the game, and the guy scores from second on it. I hadn't seen that.
"But to answer your question, sure I think that was big for him."
After the game, it was clear that Casilla's manager and teammates back him to the hilt -- not a peep of doubt in any of their voices, not a whisper of apprehension.
But the situation remains. Casilla sometimes looks like an elite closer (as he did Sunday) and sometimes looks like a guy who should be nowhere near the ninth inning (as he did in blowing three of his previous four save tries -- not all his fault, but the closer always gets the blame).
The important point is that Bochy believes in him, and that Bochy's specialty is managing and massaging his bullpen through the crucial end-of-game situations.
Bochy has done some adjusting lately; for instance, on Sunday he had Javier Lopez start the ninth to face lefty Brian Bogusevic before turning to Casilla.
After the game, Bochy said it's about the last four, five or six outs, not just the ninth inning, and added that Sergio Romo is absolutely in that mix, too.
Still, Bochy suggests that Casilla is the guy who will end up finishing these games almost every time.
An even more important point is that, with Wilson lost for the season, Casilla is by far the Giants' strongest and most elastic arm.
"Casilla's been so good for us all year," catcher Buster Posey said. "We've got the utmost confidence in him.
"He's got as good stuff as anybody on the team. Just, like I said, we've got confidence in him."
Casilla is the guy, maybe with extra help in the ninth, but most likely as the main guy.
The Giants like Romo facing selected right-handed hitters in the eighth and maybe one or two batters in the ninth, and they're going to use their lefties a batter at a time.
Then at the end, Casilla is the guy. For better, for worse, for the rest of this season.
But a stat to monitor: Sunday was his 39th appearance this season; his career high came in 2010, when he appeared in 52 games.
There is a toll on late-inning relievers, especially on the closer, and Casilla is going through it for the first time.
"I think he's had some pretty good shoes to fill when he had to fill in for Wilson," left-hander Jeremy Affeldt said. "I think he's done above and beyond."
There will be more grumbling, and there will be anxiety. But I also think Sunday was a bit of a threshold moment for Casilla's closer reign.
If there was any doubt that Bochy would go back to him and keep going back to him, there shouldn't be now. The AT&T objection has been heard, and overruled.
Contact Tim Kawakami at firstname.lastname@example.org.